AHEART March 47/3

Wang, Rui, Yuejin Wu, Guanghua Tang, Lingyun Wu, and Salma Toma Hanna. Altered L-type Ca21 channel currents in vascular smooth muscle cells from experimental diabetic rats. Am. J. Physiol. Heart Circ. Physiol. 278: H714– H722, 2000.—Vascular complications of diabetes are associated with abnormal Ca21 handling by vascular smooth muscle cells (SMCs) in which the alteration in L-type voltagedependent Ca21 channel (VDCC) currents may play an important role. In the present study, the characteristics of L-type VDCC currents in tail artery SMCs from streptozotocininduced diabetic rats were examined. The densities, but not the voltage dependence, of L-type VDCC currents were reduced as diabetes progressed from 1 wk to 3 mo. The inhibitory effect of dibutyryl-cAMP on L-type VDCC currents was greater in diabetic SMCs than in age-matched control cells (P , 0.01). Both the stimulatory effect of BAY K 8644 and the inhibitory effect of nifedipine on L-type VDCC currents were significantly enhanced in diabetic cells. The diabetes-related abnormalities in L-type VDCC currents were mimicked by culturing SMCs with a high concentration of glucose. Our results suggest that the properties of L-type VDCC in diabetic vascular SMCs were significantly altered, partially related to the increased L-type VDCC sensitivity to cAMP and hyperglycemia.