Cyclic nucleotides and contractility in human and sheep umbilical arteries

Abstract

Strips of human umbilical artery (HUA) and sheep umbilical artery (SUA) were freeze-clamped at selected times during drug-induced contraction or relaxation. Tissue concentrations of cyclic AMP and cyclic GMP were measured. 5-Hydrpxytryptamine (10 μM) contracted HUA and SUA, but had no detectable effect on cyclic GMP; cyclic AMP rose in SUA (but not in HUA) after contractions had begun. Histamine (4 gmM) elevated cyclic GMP in HUA with a time course that lagged behind contraction. Prostaglandin E 1 (PGE 1), PGE 2 and PGF 2α (2.8 μM with 0.1 % v/v ethanol) contracted HUA and decreased cyclic GMP. Nitroglycerin (3 μM) relaxed KCl-contracted HUA; this relaxation was preceded by an initial 29-fold elevation of cyclic GMP. Our data shows no consistent correlation of cyclic nucleotide changes with contraction of unbilical arteries and suggest that such changes are not essential for contraction of vascular smooth muscle. In contrast, the temporal relationship between cyclic GMP elevation and relaxation induced by nitroglycerin suggests a possible role for cyclic GMP.