Gender influences coronary L-type Ca current and adaptation to exercise training in miniature swine

Bowles, D. K. Gender influences coronary L-type Ca21 current and adaptation to exercise training in miniature swine. J Appl Physiol 91: 2503–2510, 2001.— Endurance exercise training increases smooth muscle L-type Ca21 current density in both resistance and proximal coronary arteries of female miniature swine. The purpose of the present study was to determine 1) whether gender differences exist in coronary smooth muscle (CSM) L-type Ca21 current density and 2) whether endurance training in males would demonstrate a similar adaptive response as females. Proximal, conduit (;1.0 mm), and resistance [;200 mm (internal diameter)] coronary arteries were obtained from sedentary and treadmill-trained swine of both sexes. CSM were isolated by enzymatic digestion (collagenase plus elastase), and voltagegated Ca21-channel current (ICa) was determined by using whole cell voltage clamp during superfusion with 75 mM tetraethylammonium chloride and 10 mM BaCl2. Currentvoltage relationships were obtained at test potentials from 260 to 70 mV from a holding potential of 280 mV, and ICa was normalized to cell capacitance (pA/pF). Endurance treadmill training resulted in similar increases in heart weightto-body weight ratio, endurance time, and skeletal muscle citrate synthase activity in male and female swine. ICa density was significantly greater in males compared with females in both conduit (27.57 6 0.58 vs. 24.14 6 0.47 pA/pF) and resistance arteries (211.25 6 0.74 vs. 26.49 6 0.87 pA/pF, respectively). In addition, voltage-dependent activation of ICa in resistance arteries was shifted to more negative membrane potentials in males. Exercise training significantly increased ICa density in both conduit and resistance arteries in females (27.01 6 0.47 and 29.73 6 1.13 pA/pF, respectively) but had no effect in males (28.61 6 0.50 and 212.04 6 1.07 pA/pF, respectively). Thus gender plays a significant role in determining both the magnitude and voltage dependence of ICa in CSM and the adaptive response of ICa to endurance training.