The Effects of Prostaglandin Analogues on Intracellular Ca2+ in Ciliary Arteries of Wild-Type and Prostanoid Receptor-Deficient Mice

Abstract Purpose: To clarify the mechanism of prostaglandin (PG) analogue-dependent relaxation in ciliary arteries from wild-type (WT) and prostanoid receptor-deficient mice. Methods: The intracellular-free calcium concentration ([Ca2+]i) in isolated WT mouse ciliary arteries was measured by fluorescence photometry. Reduction of [Ca2+]i leading to vascular relaxation by PG analogues latanoprost, isopropyl unoprostone, or tafluprost was compared to the maximum increase of [Ca2+]i by 50 mM KCl. The cyclooxygenase inhibitor indomethacin and the NO synthase inhibitor NG-nitro-L-arginine methylester (L-NAME) were added to investigate the involvement of vascular endothelial factors. Moreover, PG analogue-dependent reduction of [Ca2+]i was measured in ciliary artery strips from FP, EP1, EP2, and EP3 receptor-deficient mice. Results: The 3 PG analogues reduced K+-dependent increase in [Ca2+]i in a concentration-dependent manner. Indomethacin (10 μM) had little effect. The reductions of [Ca2+]i induced by 10 μM PG...