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 Watanabe<sup>1


1</sup>Departmentﾊof 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 -50ﾊmV than at -80ﾊmV. The half-maximum inhibiting concentration (IC₅₀) of troglitazone was 0.8ﾊmM with the Hill coefficient of 0.84 at -50ﾊmV HP. In contrast, the IC₅₀ value was higher than 10ﾊmM at -80ﾊmV 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