EFFECT OF U-73122 ON CALCIUM-CHANNEL ACTIVITY IN PORCINE MYOMETRIAL CELLS AND PANCREATIC BETA-CELL LINE RINM5F

AIM: To study the effect of U-73122, putative phospholipase C (PLC) in hibitor, on cytosolic Ca2+ concentration ([Ca2+](i)) and voltage-depen dent calcium channels (VDCC). METHODS: To record whole cell calcium cu rrent (I-Ca) by perforated patch-clamp and to measure cytosolic free c alcium concentration ([Ca2+](i)) with Fura-2. RESULTS: inhibited KCl-i nduced and Bay-K-8644-induced increase in [Ca2+](i) dose-dependently. U-73122 decreased markedly depolarization-induced I-Ca both in RINm5F and porcine myometrial cells in a concentration-dependent manner. The effect of U-73122 was more potent in porcine myometrial cells than tha t in RINm5F cells. U-73343 (an analog of U-73122), that does not inhib it PLC, also reduced the I-Ca by 50 %. CONCLUSION: U-73122 inhibited V DCC and [Ca2+]i in both RINm5F and porcine myometrial cells.