[Secretory function of the endothelium as a factor of vascular tone regulation in the norm and in cardiovascular pathology].

Endothelin-1 and nitric oxide are the most potent factors of the endothelium-derived substances. The factors play opposite roles in regulation of cardiovascular system, and their interaction underlies the balance of vasoconstrictor and vasodilator influences on vascular tone under normal conditions. In our experiments, changes in endothelin-1 blood concentration were associated with affected production of endogenous nitric oxide.

Endothelin antagonism does not affect adrenal catecholamine secretion and system haemodynamics during acute stress in Wistar rats.

In the present work we evaluated the role of circulating endothelin-1 (ET-1) in haemodynamics and the adrenal medulla responses to stress using PD-142893, a mixed endothelin-A- and -B- (ET(A)/ET(B)) receptor antagonist. Male Wistar rats were chronically instrumented with arterial and venous catheters and a microdialysis probe placed into the adrenal medulla. Stress was induced by a 1 h period of immobilization.

Active immunization against endothelin-1 is associated with a decrease in plasma endothelin-1 and changes in vascular reactivity.

Exogenous endothelin-1 (ET-1) or high concentrations of the peptide in pathological conditions have marked effects on vascular reactivity. In order to evaluate the role of endogenous ET-1 we investigated responsiveness of conduit (aorta) and of resistant-like (tail artery) vessels in ET-1-deficient rats. Elimination of circulating ET-1 was achieved by active immunization of Wistar rats with a peptide-haemocyanin conjugate (anti-ET-1 group), leading to a marked reduction in plasma level of the peptide in comparison with that of vehicle-treated animals (control group): 1.

Altered endothelin-dependent regulation of blood pressure and vascular tone in stress-sensitive august rats.

The endothelin (ET) system was studied in August rats, with genetically determined high sensitivity to stress, and in control Wistar rats. Radioimmunoassay revealed a significant difference in plasma endothelin-1 (ET-1) levels of August vs Wistar rats (7.1 fmol/ml vs 50.

Vasorelaxant and antiplatelet activity of 4,7-dimethyl-1,2, 5-oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide: role of soluble guanylate cyclase, nitric oxide and thiols.

1. Certain heterocyclic N-oxides are vasodilators and inhibitors of platelet aggregation. The pharmacological activity of the furoxan derivative condensed with pyridazine di-N-oxide 4,7-dimethyl-1,2, 5-oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide (FPTO) and the corresponding furazan (FPDO) was studied.