Abstract
We investigated K + currents and their regulation by the sarcoplasmic reticulum in mesenteric arterial smooth muscle cells of the spontaneously hypertensive rat (SHR). Using perforated patch-clamp technique, we found the overall K + current density was significantly lower in adult SHR compared to adult Wistar–Kyoto rats (WKY). The K + currents were almost exclusively of large-conductance Ca 2+-dependent (BK Ca) variety in SHR, but largely of voltage-gated (Kv) variety in WKY. Western blot assay showed parallel findings. These differences were not observed in pre-hypertensive rats. Depleting the intracellular Ca 2+ store inhibited the K + currents in adult SHR. Ryanodine augmented the K + current at 1 μM, but suppressed it at 10 μM; 2-aminoethoxydiphenyl borate demonstrated concentration-dependent inhibition. We conclude that an alteration of membrane K + channel composition has resulted in lower overall K + current density. The changes in K + current type may indicate an underlying defect in Ca 2+-handling that predisposes smooth muscle cells to the hypertensive phenotype.
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