SINGLE L-TYPE CALCIUM CHANNELS IN SMOOTH-MUSCLE CELLS FROM RESISTANCEARTERIES OF SPONTANEOUSLY HYPERTENSIVE RATS

The amplitude of the whole-cell L-type Ca2+ channel current recorded f rom vascular smooth muscle cells is reportedly greater in spontaneousl y hypertensive rats (SHR) than in Wistar-Kyoto rats (WKY), However, no study has examined properties of single Ca2+ channels in arterial cel ls from these strains. To further test the hypothesis that activation of L-type Ca2+ channels in arterial smooth muscle cells would be enhan ced in SHR, we recorded single Ca2+ channel currents in resistance mes enteric artery cells from SHR and WKY (8 to 9 weeks of age) using a ce ll-attached patch clamp technique, With 50 mmol/L Ba2+ in the recordin g pipette, the depolarizing pulse from a holding potential of -40 mV e voked the single L-type Ca2+ channel current. Opening of the single ch annels was more frequent in cells from SHR than from WKY. Single-chann el conductance (20 pS) and open time (1 ms at 0 mV) did not differ in the two strains, The results suggest that an increased amplitude of th e whole-cell current can be attributed to the enhanced opening of sing le Ca2+ channels in the arterial smooth muscle cells from SHR compared with WKY.