Alterations of calcium channels in vascular smooth muscle cells from spontaneously hypertensive rats

We examined the possible alterations in calcium handling through the calcium channels of spontaneously hypertensive rats (SHR) using 45Ca2+ uptake measurements in cultured aortic cells. Primary cultures of vascular smooth muscle cells (VSMC) were obtained by enzymatic dissociation of the thoracic aortas from 8-week-old SHR and age-matched Wistar-Kyoto rats (WKY). The functions of voltage sensitive calcium channels (VSCC) and receptor operated calcium channels (ROCC) were estimated from the activated 45Ca2+ uptake in VSMC with high K+ depolarization and arginine vasopressin (AVP), respectively. Compared to basal conditions, depolarization with 55 mM KCl increased 45Ca2+ uptake at 20 min by 94 +/- 17 (SE) % in SHR and 38 +/- 6% in WKY. The activated 45Ca2+ uptake was significantly greater in SHR than in WKY (p < 0.01). There was no significant difference in 45Ca2+ uptake at 20 min in the presence of 5 x 10(-8)M AVP between SHR and WKY. These results suggest that calcium uptake, at least through VSCC, is increased in VSMC of SHR. This enhanced activity may be implicated in the hypertensive mechanisms in this model of hypertension.