Showing papers in "British journal of pharmacology and chemotherapy in 1968"

Occurrence of prostaglandin e2 in the human stomach, and a study of its effects on human isolated gastric muscle

Abstract: Human stomach mucosa contains a pharmacologically active acidic lipid which is indistinguishable from (PGE2) prostaglandin E2 by chromatography in 2 different systems and by other tests. The concentrations present in mucosa are of the order of 1 mcg/g of wet tissue. Concentrations are similar in mucosa of the body and the pyloric part of the stomach; much smaller amounts are present in submucosa and muscle. PGE2 acts directly on both the longitudinal and the circular muscle layers of the human isolated stomach. The longitudinal muscle of the body of the stomach is contracted by doses of PGE2 which may be as low as 2x10 g/ml. In contrast PGE2 inhibits the contractions of circular muscle caused by acetylcholine or potassium. (Authors modified)

A simple chemical procedure for distinguishing E from F prostaglandins, with application to tissue extracts.

Abstract: An easy and relatively rapid procedure for distinguishihg the ketonic prostaglandins E (PGEs) from the nonketonic prostaglandins F (PGFs) and other hydroxy-acid lipid spasmogens is presented. The method depends on the ability of certain hydrazine derivatives to combine specifically with keto groups. Girards reagent T (trimethyl-ammonium-acetohydrazide chloride) was used for differentiation. PGFs were unaffected by the reagent whereas the reagent affected E series prostaglandins by apparently inactivating them. In addition apparent inactivation also occurred when the reagent was applied to a mixture of the PGEs and PGFs. After treatment of PGEs in aqueous solution with the reagent for 1 hour at room temperature or 0 degrees centigrade their extraction into ether on partition at pH 3-4 was reduced. Freezing to -15 degrees centigrade after the 1 hour treatment and thawing before the ether partition further reduced the recovery of PGEs. After reagent treatment in these different conditions PGFs were recovered fully. The presence of a PGE-like ketonic component in the hydroxy-acid constituents of rabbit and cat irins was demonstrated along with a lower proportion of the ketonic components in ether-purified rabbit cerebral hemisphere extract.

Influence of antimuscarinic substances on in vitro synthesis of acetylcholine by rat cerebral cortex.

Abstract: When a solution of a cholinesterase inhibitor is brought into contact with the exposed cerebral cortex or the ventricular surface of the caudate nucIeus of a living animal, acetyl- choline (ACh) is liberated into this fluid. There is an increase in the amount of ACh released when atropine is added to the solution or injected intravenously (Mitchell, 1963 ; Szerb, 1964; Polak, 1965). ',: In the following experiments the influence of atropine and some atropine-like drugs was studied on the release and synthesis of ACh by slices of cortex from rat brain, treated with a cholinesterase (ChE) inhibitor. In certain conditions atropine was found to en- hance the release of ACh from the tissue into the incubation medium and this increased release was associated with an increased synthesis of ACh. Some other antimuscarinic compounds also stimulated ACh output. I Preliminary reports of some of the results of this investigation have been published elsewhere (Polak and Meeuws, 1966; Polak, 1967).

The relaxing effect of bradykinin on intestinal smooth muscle

Abstract: Bradykinin has been found to be a potent stimulant of the adrenal medulla (Lecomte, Troquet & Dresse, 1961; Feldberg & Lewis, 1964) and sympathetic ganglia (Lewis & Reit, 1965). This effect seems to be caused by an interaction of the polypeptide with non-nicotinic receptors in ganglionic synapses (Trendelenburg, 1966) and could explain the potentiation of the hypotensive (Rocha e Silva, Corrado & Ramos, 1960; Lloyd, 1962; Nakano, 1965) and bronchoconstrictor (Collier, James & Piper, 1965) actions of bradykinin by adrenergic blockade or by adrenalectomy. It was of interest to know whether some \" sympathomimetic\" effects of bradykinin observed in isolated preparations could also be explained by a release of catecholamines; the weak cardiostimulant action of bradykinin on the isolated guinea-pig heart has been shown to be direct and not the result of a local release of catecholamines or an interaction of the polypeptide with adrenergic receptors (Antonio, 1966). In this investigation the relaxation of the isolated rat duodenum was studied, as another effect of bradykinin which resembles sympathetic stimulation. The duodenum was subjected to different ionic environments in an attempt to investigate how such relaxation is produced; epinephrine and papaverine were used for comparison.