Showing papers on "Protoporphyrin IX published in 1993"

Endogenous porphyrin distribution induced by 5-aminolaevulinic acid in the tissue layers of the gastrointestinal tract.

Abstract: The accumulation of endogenous porphyrins in rats following systemic administration of 5-aminolaevulinic acid (ALA) has been examined to assess the photosensitization characteristics of this technique for photodynamic therapy (PDT) and chemical extraction assays with fluorescence and absorbance detection of the porphyrin content have been carried out. We compared the results obtained using quantitative microfluorimetry on normal gastric and colonic tissues in rats at 0.5, 1, 2, 4 and 6 h and chemically induced duodenal tumours 2 and 4.5 h after intravenous administration of ALA at a dose of 200 mg kg-1. With chemical extraction followed by high performance liquid chromatography analysis, protoporphyrin IX (PpIX) was found to be the predominant porphyrin present, reaching peak levels of several microgrammes per gramme at 2-4 h in each type of tissue; a small amount of coproporphyrin was detected at 0.5 and 2 h in normal gastric mucosa and duodenal tumour respectively. Both the extraction assay and quantitative microfluorimetry showed that the porphyrin fluorescence builds up rapidly in the mucosal layers of the colon and stomach, reaching a maximum at 2 h, whereas lower fluorescence levels were found with a slower rate of accumulation in the corresponding muscularis layers. A significant PpIX content was found in the duodenal tumour, with a maximum of 7.1 micrograms g-1 4.5 h after ALA administration. We conclude that systemic administration of ALA can induce effective tissue sensitization with protoporphyrin IX and appears to be a promising technique for PDT.

Porphyrin Accumulation and Export by Isolated Barley (Hordeum vulgare) Plastids (Effect of Diphenyl Ether Herbicides).

Abstract: We have investigated the formation of porphyrin intermediates by isolated barley (Hordeum vulgare) plastids incubated for 40 min with the porphyrin precursor 5-aminolevulinate and in the presence and absence of a diphenylether herbicide that blocks protoporphyrinogen oxidase, the enzyme in chlorophyll and heme synthesis that oxidizes protoporphyrinogen IX to protoporphyrin IX. In the absence of herbicide, about 50% of the protoporphyrin IX formed was found in the extraplastidic medium, which was separated from intact plastids by centrifugation at the end of the incubation period. In contrast, uroporphyrinogen, an earlier intermediate, and magnesium protoporphyrin IX, a later intermediate, were located mainly within the plastid. When the incubation was carried out in the presence of a herbicide that inhibits protoporphyrinogen oxidase, protoporphyrin IX formation by the plastids was completely abolished, but large amounts of protoporphyrinogen accumulated in the extraplastidic medium. To detect extraplastidic protoporphyrinogen, it was necessary to first oxidize it to protoporphyrin IX with the use of a herbicide-resistant protoporphyrinogen oxidase enzyme present in Escherichia coli membranes. Protoporphyrinogen is not detected by some commonly used methods for porphyrin analysis unless it is first oxidized to protoporphyrin IX. Protoporphyrin IX and protoporphyrinogen found outside the plastid did not arise from plastid lysis, because the percentage of plastid lysis, measured with a stromal marker enzyme, was far less than the percentage of these porphyrins in the extraplastidic fraction. These findings suggest that of the tetrapyrrolic intermediates synthesized by the plastids, protoporphyrinogen and protoporphyrin IX, are the most likely to be exported from the plastid to the cytoplasm. These results help explain the extraplastidic accumulation of protoporphyrin IX in plants treated with photobleaching herbicides. In addition, these findings suggest that plastids may export protoporphyrinogen or protoporphyrin IX for mitochondrial heme synthesis.

Cellular Localization of Protoporphyrinogen-Oxidizing Activities of Etiolated Barley (Hordeum vulgare L.) Leaves (Relationship to Mechanism of Action of Protoporphyrinogen Oxidase-Inhibiting Herbicides)

Abstract: Seven-day-old, etiolated barley (Hordeum vulgare L. var Post) leaves were fractionated into crude and purified etioplast, microsomal, and plasma membrane (PM) fractions. Protoporphyrinogen oxidase (Protox) specific activities of crude etioplast, purified etioplast, microsome, and PM fractions were approximately 29, 26, 23, and 12 nmol h-1 mg-1 of protein, respectively. The herbicide acifluorfen-methyl (AFM), at 1 [mu]M, inhibited Protox activity from crude etioplasts, purified etioplasts, microsomes, and PM by 58, 59, 23, and 0% in the absence of reductants. Reductants (ascorbate, glutathione [GSH], dithiothreitol [DTT], and NADPH) individually reduced the Protox activity of all fractions, except that microsomal Protox activity was slightly stimulated by NADPH. Ascorbate, GSH, or a combination of the two reductants enhanced Protox inhibition by AFM, and AFM inhibition of Protox was greatest in all fractions with DTT. NADPH enhanced AFM inhibition significantly only in etioplast fractions. Uroporphyrinogen I (Urogen I) and coproporphyrinogen I (Coprogen I) oxidase activities were found in all fractions; however, etioplast fractions had significantly more substrate specificity for protoporphyrinogen IX (Protogen IX) than the other fractions. Urogen I and Coprogen I oxidase activities were unaffected by AFM in all fractions, and 2 mM DTT almost completely inhibited these activities from all fractions. Diethyldithiocarbamate inhibited PM Protox activity by 62% but had less effect on microsome and little or no effect on etioplast Protox. Juglone and duroquinone stimulated microsomal and PM Protox activity, whereas the lesser effect of these quinones on etioplast Protox activity was judged to be due to PM and/or microsomal contaminants. These data indicate that there are microsomal and PM Protogen IX-oxidizing activities that are not the same as those associated with the etioplast and that these activities are not inhibited in vivo by AFM. In summary, these data support the view that the primary source of high protoporphyrin IX concentrations in AFM-treated plant tissues is from Protogen IX exported by plastids and oxidized by AFM-resistant extraorganellar oxidases.

In vivo photoproduct formation during PDT with ALA-induced endogenous porphyrins

Abstract: The administration of 5-aminolevulinic acid (ALA) in tumor-bearing nude mice leads to the formation of the fluorescent, photounstable photosensitizer protoporphyrin IX in tumor tissue. On-line fluorescence spectroscopy during photodynamic therapy (PDT) shows the in vivo formation of chlorintype photoproducts of protoporphyrin. The fluorescence of protoporphyrin as well as its photoproducts is bleached completely at the end of the PDT (100 J cm-2, 630 nm). These findings were also verified using ultrashort laser pulses and time-correlated single-photon counting. A photinduced shortening of the decay times and decrease in the integral fluorescence intensity were measured in vivo due to the photodestruction of the endogenous photosensitizer protoporphyrin IX in the tumor.

Investigation of the subcellular location of the tetrapyrrole-biosynthesis enzyme coproporphyrinogen oxidase in higher plants

Abstract: The subcellular location of two enzymes in the biosynthetic pathway for protoporphyrin IX, coproporphyrinogen (coprogen) oxidase (EC 1.3.3.3) and protoporphyrinogen (protogen) oxidase (EC 1.3.3.4) has been investigated in etiolated pea (Pisum sativum) leaves and spadices of cuckoo-pint (Arum maculatum). Plant tissue homogenized in isotonic buffer was subjected to subcellular fractionation to prepare mitochondria and plastids essentially free of contamination by other cellular organelles, as determined by marker enzymes. Protogen oxidase activity measured fluorimetrically was reproducibly found in both mitochondria and etioplasts. In contrast, coprogen oxidase could be detected only in etioplasts, using either a coupled fluorimetric assay or a sensitive radiochemical method. The implications of these results for the synthesis of mitochondrial haem in plants is discussed.

Nucleotide sequence of the hemG gene involved in the protoporphyrinogen oxidase activity of Escherichia coli K12.

Abstract: The hemG gene of Escherichia coli K12 is involved in the activity of protoporphyrinogen oxidase, the enzyme responsible for the conversion of protoporphyrinogen IX into protoporphyrin IX during hem...

Photochemotherapeutic method using 5-aminolevulinic acid and precursors thereof

Abstract: Medicaments for detecting and treating malignant and non-malignant tissue abnormalities and lesions of the skin; conjunctiva; respiratory, digestive and vaginal mucosa; endometrium and urothelium; and for ablating the endometrial tissue and treating body fluids containing suspended abnormal cells, and for treating cancers of the nervous system are prepared from 5-aminolevulinic acid or precursor thereof and subsequently administered to the patient in an amount sufficient to induce syntheses fluorescence and/or photosensitizing concentrations or protoporphyrin IX in the abnormal cells, followed by exposure of the abnormal cells to light of photoactivating wavelengths

Intrauterine 5-aminolevulinic acid induces selective fluorescence and photodynamic ablation of the rat endometrium

Abstract: — 5-Aminolevulinic acid (ALA), a precursor of protoporphyrin IX (Pp IX), was administered into the rat uterine cavity in an attempt to selectively ablate the endometrium. Doses of ALA ranging from 4 to 50 mg were injected into one uterine horn of rats while the vehicle (saline) was injected into the contralateral horn. Animals were divided into three groups. In group one, the uterine horns were removed and processed for either fluorescent mi- croscopy or spectrophotofluorometry 3 h later. In group two, rats were allowed to survive for either 2 or 10 days, and then the uterine horns were harvested and processed histologically. In group three, both uterine horns were exposed to transmural light (approximately 150 J/cm*) 3 h after administration of ALA or saline and processed histologically either 2 or 10 days later. Fluorescent microscopy showed fluorescence in the endometrium and not in the myometrium. The maximum emission spectra of endometrial fluorescence occurred at 630 and 690 nm, characteristic of Pp IX. In contrast, no fluorescence was detected in saline-treated uterine horns. Light exposure resulted in extensive damage only to the ALA-treated endometrium. There was no indication of regeneration 10 days after treatment. We conclude from these studies that ALA administered into the lumen of the rat uterus is selectively converted into Pp IX within the endometrium. Furthermore, photoactivation of the Pp IX results in selective ablation of the endometrium.

A comparative pressure tuning hole burning study of protoporphyrin IX in myoglobin and in a glassy host

Abstract: We measured the behavior of spectral holes under isotropic pressure changes as a function of burn frequency. We compared a protein sample, namely protoporphyrin IX substituted myoglobin in a glycerol/water glass with a sample where the protoporphyrin IX was directly dissolved in a host glass. The differences are remarkable—holes in the pure glass behave as expected for a homogeneous isotropic material. It is the nonlinear frequency dependence of the pressure shift where the deviation of the protein sample is most obvious. These observations signal a correlation between the structures of the dye probe and the structures of the apoprotein. They further show that global parameters of the apoprotein, such as the isothermal compressibility, depend strongly on the associated conformational substates and are subject to unexpected large variations.

The study of endogenous porphyrins in human skin and their potential for photodynamic therapy by laser induced fluorescence spectroscopy

Abstract: Human skin shows a strong autofluorescence in the red spectral region when excited by the 407 nm radiation of a krypton ion laser. The spectrum consists of three main peaks around 600, 620 and 640 nm, which are typical for metalloporphyrins such as Zn-protoporphyrin, coproporphyrin and free protoporphyrin IX, and perhaps represent a mixture of these compounds. The fluorescence is located in sebaceous follicles which contain large amounts of the porphyrin-producing skin bacterium Propionibacterium acnes. Irradiation, especially with violet light, reduces both the integral fluorescence intensity and the number of living bacteria. The process of photobleaching is oxygen-dependent. In addition, irradiation results in the formation of fluorescent photoproducts with spectral bands similar to photo-protoporphyrin. It seems to be possible to use the endogenous porphyrins for a photodynamic therapy of acne vulgaris and to monitor the therapeutic effect by the simultaneous measurement of spectral changes.

Comparative effects of heme and metalloporphyrins on interferon-gamma-mediated pathways in monocytic cells (THP-1).

Abstract: Previous results have demonstrated links between cell-mediated immunity, interferon (IFN)-gamma and neopterin production with heme, porphyrins, and iron metabolism. In this study, we compared the effects of heme, several metalloporphyrins, protoporphyrin IX, and iron on the signal or IFN-gamma-mediated pathways, such as the expression of major histocompatibility complex class II antigens, neopterin formation, and the degradation of tryptophan. Using the human monocytic cell line, THP-1, we found that heme, Zn-mesoporphyrin, Zn-deuteroporphyrin, Co-protoporphyrin, and iron reduced the efficiency of the IFN-gamma signal. In addition, Zn-mesoporphyrin almost fully inhibited IFN-gamma-induced degradation of tryptophan by the heme protein, indoleamine 2,3-dioxygenase. In contrast, tin-protoporphyrin enhanced the IFN-gamma effects as seen by increased neopterin production, enhanced tryptophan degradation, and elevated HLA-DR antigen expression on cells. These effects are considered to be due to the action of heme, metalloporphyrins, iron, or heme byproducts on the IFN-gamma signal, rather than to direct effects on IFN-gamma-induced enzymatic pathways. Heme and metalloporphyrins were previously shown to affect heme oxygenase activity, T cell growth, and lipid peroxidation and to modulate interleukin 2 activity. These pathways are also known to be influenced by IFN-gamma, and our data suggest that heme and metalloporphyrins may directly modulate the efficiency of the IFN-gamma signal.

Lipid–porphyrin fibres: morphology and incorporation into phospholipid vesicle

Abstract: Protoporphyrin IX derivatives having two alkylphosphocholine groups (lipid–porphyrins) forms stable fibrous aggregates in aqueous medium; fibres have been spontaneously incorporated into the bilayer of the phospholipid vesicle.

Chemically induced chromosome damage in early-developing embryos of Anilocra physodes L. (Crustacea, Isopoda) following exposure to bis[dimethyltin(IV)chloro]protoporphyrin IX

Abstract: In order to obtain chromosome preparations from early-developing embryos of Anilocra physodes, a squash technique has been successfully employed. Results gathered after exposure of this material to bis[dimethyltin(IV)chloro]protoporphyrin IX {[(CH3)2SnCl]2 - Protoporphyrin IX} solutions at different exposure times suggest that this chemical complex is capable of producing abnormal metaphase and anaphase figures in proportion to its concentration and not to exposure length. Essentially, all of the chromosome abnormalities are classifiable as chromosome fragments mainly observed at the metaphase stage; chromosome bridges; and large decondensed chromosome regions.

Molecular and genetic characterization of ferrochelatase.

Abstract: Ferrochelatase (heme synthase, protoheme ferrolyase [EC 4.99.1.1]), the final enzyme of the heme biosynthetic pathway, catalyzes the insertion of ferrous ion into protoporphyrin IX to produce protoheme IX. The thorough understanding of the enzyme is prerequisite to elucidating the regulation of iron and heme metabolism. The enzyme's activity is found on the inner mitochondrial membrane of a variety of mammalian cells. The enzyme catalyzes the chelation not only of iron but also of divalent metal ions including cobalt and zinc, and the activity is affected by various metals and lipids. The molecular weights of eukaryotic ferrochelatases are 40,000-42,000 daltons. Complementary DNA (cDNA) encoding ferrochelatase from mouse, human, yeast and bacteria have been isolated, and the derived amino acid sequences show 27-88% homologies among species. The expression of ferrochelatase seems to occur in all living cells, and to play an important role in the regulation of heme biosynthesis. Ferrochelatase is markedly induced at the transcriptional level during erythroid differentiation when iron uptake by cells and hemoglobin synthesis are upregulated. This induction can be explained by the existence of sequences characteristic of erythroid-related genes. The gene has been mapped to human chromosome 18q21.3 and contains 11 exons with a size of about 45 kilobases. Once the gene for human ferrochelatase is cloned, the molecular basis and clinical diagnosis of erythropoietic protoporphyria, caused by a deficiency of ferrochelatase, will become possible. This review summarizes recent advances in ferrochelatase research and suggests important subjects for future research.

Protection by cloned carotenoid genes expressed in Escherichia coli against phototoxic molecules activated by near-ultraviolet light.

Abstract: Publisher Summary This chapter reviews the evidence that carotenoids protect plants, animals, and microorganisms against photodynamic action by quenching triplet state photosensitizers, ringlet oxygen, and radical oxygen species Photosynthetic bacteria contain carotenoids that serve to protect against photodynamic action probably involving chlorophyll as an endogenous photosynthesizer In the non-photosynthetic bacterium, Myxococcus xanthus , protoporphyrin IX accumulates to high levels when the cells enter stationary phase Concomitant with the accumulation of protoporphyrin IX, carotenoids are synthesized probably to protect against photodynamic action resulting from protoporphyrin IX, serving as an endogenous photosensitizer Epiphytic and phytopathogenic bacteria associated with above ground plant parts frequently produce yellow pigments, presumably carotenoids, to protect against photodynamic damage that may result from the absorption of visible light by the chlorophyll of the host plant acting as a photosensitizer Many fungi produce carotenoids, and in the case of Neurospora crassa , these pigments have been shown to protect against photodynamic action involving specific exogenous dyes

Photodynamic diagnosis following intravesical instillation of aminolevulinic acid (ALA): first clinical experiences in urology

Abstract: Delta Aminolevulinic acid (ALA), a precursor of Protoporphyrin IX (PP IX) in hem biosynthesis has been topically applied in urinary bladders in order to study its potential as fluorescent tumor marker. Preclinical experiments have been performed on chemically induced tumors in rats, revealing a ratio of PP IX-fluorescence intensity up to 20:1 in tumors as compared to healthy urothelium. Synthesis of PP IX has been stimulated in 56 patients by intravesical instillation of a pH-neutral ALA-solution. After an incubation time of two to four hours strong red fluorescence was endoscopically observed even in tiny superficial tumors. Brightness and contrast allows visualization of early stage urothelial diseases with naked eyes and without the necessity suppressing background fluorescence or violet excitation light.

Stimulation of appearance of extraplastidic tetrapyrroles by a photooxidative treatment of the plastids

Abstract: In the mustard seedling (Sinapis alba L.) the appearance of photodetectable phytochrome and synthesis of relatively abundant cytosolic hemoproteins (nitrite reductase, ascorbate peroxidase) are stimulated rather than impaired by a photooxidative treatment of the plastids. While the ability to synthesize protoporphyrin IX from exogenous 5-aminolevulinic acid was preserved in the photooxidatively damaged plants, protochlorophyll and chlorophyll accumulation was no longer possible. It appears from our data that in higher plants the pathway of tetrapymole synthesis up to protoporphyrin IX is not adversely affected by a photooxidative treatment of the plastids that destroys the capacity of the organelle to synthesize chlorophyll.

Organometallic complexes with biological molecules. I: Diorganotin(IV)chloro protoporphyrin IX complexes: solid-state and solution-phase characterization

Abstract: Protoporphyrin IX (H4PPIX) complexes of diorganotin(IV)chloro moieties with formula (R2SnCl)2H2PPIX (RMe, Bu and Ph) have been obtained and their solid-state and solution-phase configurations have been studied through spectroscopic investigations. Coordination of the side-chain carboxylates of H4PPIX to R2Sn(IV)Cl moieties, with bridging carboxylate (COO−) has been inferred by comparison of the free and coordinated H4PPIX IR spectra, while the occurrence of a five-coordinated tin(IV) atom in a cis-R2 trigonal bipyramidal structure has been deduced, for all of the synthesized complexes, by rationalization of the nuclear quadrupole splitting parameters, according to the point-charge model formalism. Fanally, the solution-phase spectral features of (R2SnCl)2−H2PPIX are in agreement with the monomeric character of the protoporphyrin IX, under the experimental conditions used.

Method for the rapid removal of protoporphyrin from protoporphyrin IX-containing solutions of hemoglobin

Abstract: The present invention relates to a method for the production of a substantially protoporphyrin IX free hemoglobin solution comprising: rapidly heating a crude protoporphyrin IX-containing hemoglobin solution for a relatively short time and at a relatively high temperature to reduce protoporphyrin IX-containing hemoglobin to insignificant levels in said protoporphyrin IX-containing hemoglobin solution.

Synthesis and Aggregate Morphology of Protoporphyrin IX Derivative Having Phospholipid Residue

Abstract: A protoporphyrin IX derivative having a phospholipid residue (lipid-porphyrin) was synthesized. The lipid-porphyrin itself formed an oval multilamellar vesicle in an aqueous medium. The spectral features of the lipid-porphyrin vesicle indicated a stacked configuration of the porphyrin moiety.

Effect of Diphenyl Ether Herbicides

Abstract: We have investigated the formation of porphyrin intermediates by isolated barley (Hordeum vulgare) plastids incubated for 40 min with the porphyrin precursor 5-aminolevulinate and in the presence and absence of a diphenylether herbicide that blocks protoporphyrinogen oxidase, the enzyme in chlorophyll and heme synthesis that oxidizes protoporphyrinogen IX to protoporphyrin IX. In the absence of herbicide, about 50% of the protoporphyrin IX formed was found in the extraplastidic medium, which was separated from intact plastids by centrifugation at the end of the incubation period. In contrast, uroporphyrinogen, an earlier intermediate, and magnesium protoporphyrin IX, a later intermediate, were located mainly within the plastid. When the incubation was carried out in the presence of a herbicide that inhibits protoporphyrinogen oxidase, protoporphyrin IX formation by the plastids was completely abolished, but large amounts of protoporphyrinogen accumulated in the extraplastidic medium. To detect extraplastidic protoporphyrinogen, it was necessary to first oxidize it to protoporphyrin IX with the use of a herbicide-resistant protoporphyrinogen oxidase enzyme present in Escherichia coli membranes. Protoporphyrinogen is not detected by some commonly used methods for porphyrin analysis unless it is first oxidized to protoporphyrin IX. Protoporphyrin IX and protoporphyrinogen found outside the plastid did not arise from plastid lysis, because the percentage of plastid lysis, measured with a stromal marker enzyme, was far less than the percentage of these porphyrins in the extraplastidic fraction. These findings suggest that of the tetrapyrrolic intermediates synthesized by the plastids, protoporphyrinogen and protoporphyrin IX, are the most likely to be exported from the plastid to the cytoplasm. These results help explain the extraplastidic accumulation of protoporphyrin IX in plants treated with photobleaching herbicides. In addition, these findings suggest that plastids may export protoporphyrinogen or protoporphyrin IX for mitochondrial heme synthesis.

Design of PDT protocols using delta-aminolevulinic acid (5ALA)

Abstract: The kinetics of protoporphyrin IX (PPIX) synthesis, bioconversion to other metabolic products, and photobleaching were measured in cell cultures after incubation in media containing the metabolic precursor for heme synthesis, (delta) -aminolevulinic acid (5 ALA). A compartmental model described the kinetics in terms of rate constants for the three processes. The maximum amount of PPIX that can be attained in the cells and the concentration of 5 ALA in the medium that obtains this maximum were determined. Using this information, two dosimetry protocols are outlined which both involve complete photobleaching of the PPIX: (1) the classical acute protocol using maximum 5 ALA to produce maximum PPIX and a light treatment of about 0.5 - 1 hr, and (2) a novel prolonged protocol using continuous low-level 5 ALA delivery to produce only slightly elevated PPIX and an extended light exposure time of over 24 hrs.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Effects of n-phenylimide s-23142 and n-methyl mesoporphyrin ix on the synthesis of the phytochrome chromophore in pea embryonic axes

Abstract: Treatment of imbibed embryonic axes taken from seeds of Pisum sativum with N-phenylimide S-23142, a herbicide that has been suggested to inhibit protoporphyrin synthesis, or with N-methyl mesoporphyrin IX, an inhibitor of the iron chelatase for heme, resulted in a significant decrease in the amount of spectrophotometrically detectable phytochromc in the axes in both cases. However, the amount of immunochemically detectable phytochrome was not affected by either treatment. If S-23142 inhibits the synthesis of protoporphyrin IX in pea, it appears that the conversion of protoporphyrinogen IX to protoporphyrin IX is involved in the biosynthesis of the phytochrome chromophore. The conversion of protoporphyrin IX to heme (Fe-protoporpbyrin) also appears to be a step in the biosynthesis of the chromophore, since N-methyl mesoporphyrin IX prevented the synthesis of spectrophotometrically detectable phytochrome but did not affect the magnesium chelatase activity required for the synthesis of chlorophyll in pea embryonic axes. The results suggest that protoporphyrinogen IX, protoporphyrin IX and heme are intermediates in the biogenesis of the phytochromc chromophore. The pathway to phytochromobilin might become fixed after protoporphyrin IX, being directed toward the Fe branch for heme rather than to the Mg branch for chlorophyll.

An elevated hematogenous photosensitizer in the preterm neonate

Abstract: PURPOSE Human blood contains low levels of protoporphyrin IX (PP IX), a photoactive compound that produces reactive oxygen species when exposed to light It has been proposed that photoactivation of PP IX and subsequent generation of potentially tissue-damaging reactive oxygen may be a mechanism of retinal injury in retinopathy of prematurity (ROP) The purpose of this study is to determine an association between blood PP IX level and infant birth-weight and gestational age METHODS Erythrocyte PP IX levels were measured from the umbilical cord blood of 31 neonates, both full term and preterm Birthweights and gestational ages were recorded RESULTS PP IX levels in infants weighing 1000 grams (125 micrograms/dl, n = 24; P < 002) CONCLUSION Elevated PP IX levels may place preterm neonates at increased risk for photosensitizing retinal injury