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) inhibitor, on cytosolic Ca2+ concentration ([Ca2+]i) and voltage-dependent calcium channels (VDCC).


METHODS
To record whole cell calcium current (ICa) by perforated patch-clamp and to measure cytosolic free calcium concentration ([Ca2+]i) with Fura-2.


RESULTS
U-73122 inhibited KCl-induced and Bay-K-8644-induced increase in [Ca2+]i dose-dependently. U-73122 decreased markedly depolarization-induced ICa 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 that in RINm5F cells. U-73343 (an analog of U-73122), that does not inhibit PLC, also reduced the ICa by 50%.


CONCLUSION
U-73122 inhibited VDCC and [Ca2+]i in both RINm5F and porcine myometrial cells.