Jpn. J. Pharmacol. 82 (2), 102-109 (2000)

Inhibitory Action of Troglitazone, an Insulin-Sensitizing Agent,
on the Calcium Current in Cardiac Ventricular Cells of Guinea Pig

Yoko Katoh1, Shigeatsu Hashimoto1, Junko Kimura2 and Tsuyoshi Watanabe1

1DepartmentÊof Internal Medicine III, 2Department of Pharmacology,
Fukushima Medical University, School of Medicine, 1 Hikarigaoka, Fukushima 960-1295, Japan

Abstract: We investigated the effects of troglitazone, a new orally active hypoglycemic agent, on the voltage-dependent L-type Ca2+ current in single cardiac ventricular myocytes of guinea pigs by the whole-cell voltage clamp technique. Troglitazone blocked the Ca2+ currents in a concentration-dependent manner. The inhibitory effect was more potent at the holding potential (HP) of -50ÊmV than at -80ÊmV. The half-maximum inhibiting concentration (IC50) of troglitazone was 0.8ÊmM with the Hill coefficient of 0.84 at -50ÊmV HP. In contrast, the IC50 value was higher than 10ÊmM at -80ÊmV HP. These results suggest that troglitazone at therapeutic concentrations inhibit the Ca2+ channels and may exert cardioprotective effects in diabetic conditions.

Keywords: Troglitazone, Ca2+ channel, Cardiac myocyte, Patch-clamp, Diabetes

Copyright© The Japanese Pharmacological Society 2000

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