The role of angiotensin converting enzyme in the metabolism of bradykinin and angiotensin I by in vitro human basilar artery and rabbit aorta was studied. On both human basilar artery and rabbit aorta concentration-effects curves to angiotensin I were significantly attenuated by captopril at a concentration which had no effect on bradykinin responses on both tissues. The metabolism of bradykinin and angiotensin I was studied using high performance liquid chromatography. Both peptides were broken down by human basilar artery and rabbit aorta in a similar fashion. The breakdown of angiotensin I but not bradykinin was significantly attenuated by captopril. 1,10-phenanthroline did attenuate breakdown of bradykinin but this was found not to be significant compared with controls. The results confirm that angiotensin converting enzyme is present in both these tissues and is important for the conversion of angiotensin I to angiotensin II. It appears that other peptidases are important in the breakdown of kinins by these tissues and should be taken into account when investigating the mechanism of action of such peptides on these vascular preparations.
1 Experiments were performed to determine the effects of fibrin(ogen) degradation products on the following in vitro vascular preparations: rabbit aortic strip, rat aortic strip and human basilar arterial strip. 2 Citrated plasma and streptokinase were incubated at 37°C to produce a crude preparation of fibrinogen degradation products and 0.1 ml aliquots were removed at various time intervals. These samples were tested for intrinsic activity and possible interactions with EC and threshold concentrations of 5-hydroxytryptamine on the vascular preparations. 3 Enhancement of the responses obtained by both concentrations of 5-hydroxytryptamine was produced by samples taken throughout the streptokinase incubation period, the maximum effect being seen at 90 min. 4 The 90 min incubate produced volume-dependent (25-400 p1) potentiations of the responses developed in the three vascular preparations to the ECSO and threshold concentrations of 5-hydroxytryptamine. 5 It is suggested that fibrin(ogen) degradation products may be involved in the intense vasoconstriction of the cerebral arteries following subarachnoid haemorrhage.
Experiments were performed to assess the ability of bencianol (ZY15051) to reverse contractions of human basilar arteries in vitro that were induced by a wide range of substances implicated in the aetiology of migraine and cerebral arterial spasm. Bencianol caused a dose-related (1-100 micrograms ml-1) reversal of contractions induced by 5-hydroxytryptamine, noradrenaline, angiotensin II, prostaglandin F2 alpha, and U-46619 (a thromboxane-A2 mimetic). Bencianol was more effective against contractions induced by EC50 compared to maximal concentrations of each agent, and was least effective against the thromboxane-A2 mimetic, U-46619. In addition, contractions induced by thromboxane-A2-like substances generated from guinea-pig lungs were also reversed by bencianol but only at the highest concentration used (100 micrograms ml-1). The relevance of this action of bencianol to migraine and cerebral arterial spasm is discussed.
The kininogen content of rat plasma during late pseudopregnancy was found to increase, showing similar but less marked changes to those found in normal pregnancy and parturition. The kininase values during pseudopregnancy showed no significant change from the non-pregnant control value. During the condition of 'pseudoparturition', in which the fetuses were killed in utero between Days 12 and 15 of pregnancy and the placentae were delivered on Day 21 or 22, the kininogen content of the plasma increased. The increase in plasma kininogen during 'pseudoparturition' was more marked than in pseudopregnancy. The kininase activity during 'pseudoparturition' was significantly lower than that found in non-pregnant female rats ; this finding is similar to that observed in pregnant rats. It appears from these findings that the changes in the kinin system components during pregnancy are not wholly dependent on the fetoplacental unit.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.