Differential distribution of mechanosensitive nonselective cation channels in systemic and pulmonary arterial myocytes of rabbits.

The mechanosensitive nonselective cation channel (NSC(MS)) is a key player in vascular myogenic contraction. The functional channel density and pressure sensitivity of NSC(MS) in vascular myocytes were compared between pulmonary and systemic arteries (coronary, mesenteric and cerebral arteries) in the rabbit. In cell-attached condition, a negative pressure via patch pipettes commonly activated NSC(MS) with weak voltage dependence. The threshold pressure for activation was lower, and the density of NSC(MS) was higher in the pulmonary than the systemic arteries. When the pulmonary arteries were divided into small-diameter (outer diameter, OD < 0.5 mm) and large-diameter (OD > 1.5 mm) arteries, the low threshold and high density of NSC(MS) were observed only in small-diameter ones. No such difference was observed between the small- and large-diameter coronary arteries. The higher stretch sensitivity and denser functional expression of NSC(MS) in small pulmonary arteries might suggest an adaptive tuning for the relatively low pulmonary blood pressure in vivo.