Effects of pioglitazone on calcium channels in vascular smooth muscle.
Pioglitazone, an insulin-sensitizing, antidiabetic agent, has blood pressure-lowering effects in insulin-resistant hypertensive rats and attenuates growth factor-induced increases of intracellular Ca2+ in rat aortic vascular smooth muscle cells. To determine whether modulation of voltage-dependent Ca2+ channels plays a role in this association, we investigated the effects of pioglitazone on voltage-dependent current in cultured rat aortic (a7r5) and freshly dissociated rat tail artery vascular smooth muscle cells. Both cell types were studied with whole-cell patch-clamp techniques. Current through L-type Ca2+ channels was elicited with a voltage ramp in the presence of Ba2+ substituted for Ca2+. T-type Ca2+ current was studied using a two-pulse protocol that enabled the isolation of transient current. In a7r5 vascular smooth muscle cells, 2-minute application of pioglitazone (5 and 10 mumol/L) reduced L-type current by 7.9 +/- 1.0% (n = 8) (mean +/- SEM, number of cells) and 14.5 +/- 3.0% (n = 9) (P < .01, two-tailed paired t test), respectively. In contrast, 2-minute application of pioglitazone had no significant effect on T-type Ca2+ current. In freshly dissociated tail artery vascular smooth muscle cells, 2-minute application of 10 mumol/L pioglitazone had an insignificant effect (4.8 +/- 5.6% reduction); however, 25 mumol/L pioglitazone reduced L-type current by 27.3 +/- 7.2% (n = 5) (P < .01). Two-minute application of 0.1% or 0.2% dimethyl sulfoxide (vehicle) alone had no significant effects on currents in either type of vascular smooth muscle cell.(ABSTRACT TRUNCATED AT 250 WORDS)
Zhang
F
F
Department of Physiology, Wayne State University, School of Medicine, Detroit, MI.
Sowers
J R
JR
Ram
J L
JL
Standley
P R
PR
Peuler
J D
JD
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D000077205:Pioglitazone; D051381:Rats; D017207:Rats, Sprague-Dawley; D013844:Thiazoles / Q000494:pharmacology*; D045162:Thiazolidinediones
D015220:Calcium Channels; D007004:Hypoglycemic Agents; D013844:Thiazoles; D045162:Thiazolidinediones; D000077205:Pioglitazone; D004121:Dimethyl Sulfoxide