Key result
BAY K 8644 increases L-type calcium channel currents ~2-fold in rat arterial smooth muscle cells.
This preclinical study characterizes T-type and L-type calcium channels in rat tail artery smooth muscle cells, highlighting their distinct electrophysiological properties and pharmacological responses.
Rat tail artery data characterize vascular Ca channels; extends preclinical models but leaves clinical translation open.
Whole cell patch-clamp recordings were carried out on smooth muscle cells from rat tail artery in short-term culture to verify the existence of and to characterize the calcium channels that are present. Two types of voltage-dependent calcium channels were identified in 55 of 63 cells studied. The T-type calcium channel was activated at -50 mV, and the peak inward current occurred at -10 mV, whereas the L-type channel was activated at -20 mV, and the peak inward current occurred at +10 or +20 mV. The T-type channel current inactivated quickly in contrast to the much slower inactivation of the L-channel current. The voltage dependence of steady-state inactivation of the two channels was similar to that reported for other vascular smooth muscle preparations. An internal solution containing Cs2-aspartate maintained the calcium-channel currents for at least 20 min with only a 5-10% decline. BAY K 8644 had no effect on T-channel currents, but the L-channel current was increased by at least a factor of two. In addition, BAY K 8644 shifted the activation threshold, the peak inward current, and the steady-state inactivation-activation curves of L-type channel currents in the direction of hyperpolarization.
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Wang et al. (1989) studied this question. BAY K 8644 was evaluated on Calcium channel currents (T-type and L-type). Two types of voltage-dependent calcium channels (T-type and L-type) were identified in rat tail artery smooth muscle cells, with BAY K 8644 increasing L-channel currents by at least a factor of two.
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