Responses of arterial smooth muscle from normotensive and pre-eclamptic subjects to the calcium channel agonist, Bay K 8644

The effect of Bay K 8644, a dihydropyridine Ca²⁺ agonist, on in vitro contractile responses of inferior epigastric arteries from normotensive (N) and pre-eclamptic (P) subjects has been investigated, with a view to further defining the mechanism of the increased vascular sensitivity associated with pregnancy-induced hypertension. Bay K 8644 (10^-10-10^-7M) caused dose-dependent contractions of N as well as P arteries under resting conditions in the order: P > N and caused development of rhythmic contractions in both N and P arteries. Bay K 8644 effects were prevented by 3 × 10^-8M Nifedipine (a Ca⁺² antagonist). Bay K 8644 also significantly (P < 0.05) enhanced the sensitivity as well as maximal contractile responses to CaCl₂ in 40 m M K⁺-depolarized Ca-depleted N and P arteries in the order: P > N. The results suggest that the increased peripheral vascular sensitivity associated with pregnancy-induced hypertension may be due, at least in part, to enhanced activity of the potential-sensitive Ca²⁺ channels in arterial smooth muscle plasmalemma.