Showing papers by "Ivanka Markovic published in 1998"

The effects of NO synthesis inhibition on the uptake of endogenous nucleosides into the rat brain

Abstract: Brain uptake of 3H endogenous nucleosides in rats was measured by Brain Uptake Index method, using 14C-sucrose as a referent molecule. The values obtained in control group were 4.68±0.93 for adenosine, 4.10±0.72 for guanosine and 1.14±0.72 for thymidine, indicating significant blood-to-brain transport of purine nucleosides. NO-synthase inhibition was induced by i.p. application of 25 mg/kg 1-ω-nitro-arginin methyl ester (L-NAME) and 5mg/kg diphenylethiodonium (brain parenchyma NOS inhibitor). HPLC analysis showed that the concentration of L-NAME in brain was sufficient to cause inhibition of NOS. Application of L-NAME resulted in significant inhibition of brain uptake for both purine nucleosides. Unlike adenosine, in the case of guanosine a correlation between the rate of brain uptake inhibition and the L-NAME concentration in plasma, but not in brain, was obtained. Application of diphenylethiodonium also caused a significant decrease in both guanosine and adenosine brain uptake. The obtained results were not significantly different from the BUI values obtained after preapllication of L-NAME. Our results suggest that NOS inhibition decreases brain uptake of purine nucleosides. Such effect(s) are probably due to the inhibition of brain parenchyma NOS.