Effects of Nitroglycerin on Stable Thromboxane A₂ Analogue-Induced, Nifedipine-Resistant Contraction in Canine Basilar Artery

Abstract

The stable thromboxane A₂ analogue, STA₂, caused concentrationdependent contractions in the canine basilar artery. In Ca²⁺-free medium containing EGTA (0.1 mM) and nifedipine (10^-6 M), the addition of Ca²⁺ (2.5 mM) in the presence of STA₂ (10^-8 M) caused a tonic contraction (nifedipine-resistant Ca²⁺-induced contraction). In the basilar artery, nitroglycerin did not significantly affect such nifedipine-resistant Ca²⁺-induced contractions, but nearly abolished the contraction in the coronary artery. The present experiments suggest that the regulatory mechanism of mobilized Ca²⁺ for the nifedipine-resistant Ca²⁺-induced contraction produced by STA₂ in the basilar artery is different from that in the coronary artery.