Effect of depolarizing and hyperpolarizing agents on the membrane potential difference of primary cultures of rabbit aorta vascular smooth muscle cells.

Vascular smooth muscle cells of rabbit aorta were enzymatically dispersed, kept in primary culture, and studied between days 1 and 7 in a bath rinsed with Ringer-like solution at 37 degrees C. The electrical membrane potential difference (PD) was measured with microelectrodes. The mean value of PD was -50 +/- 0.4 mV (n = 53). Cromakalim (BRL 34915), 1 mumol/l and 10 mumol/l, hyperpolarized the membrane potential by 9 +/- 1 mV (n = 11) and 15 +/- 1 mV (n = 53) respectively. Glibenclamide (10 mumol/l) abolished the hyperpolarizing effect of chromakalim (n = 6). Simultaneous addition of cromakalim and glibenclamide (both 10 mumol/l, n = 11) and glibenclamide itself (10 mumol/l, n = 7) had no effect on PD. In patch-clamp experiments in outside-out-oriented Ca(2+)-sensitive K+ channels, cromakalim increased the open probability (Po) only slightly and only with a cytosolic Ca2+ activity of 1 mumol/l. In all other series cromakalim had no effect on the Po of these channels. Forskolin (10 mumol/l) hyperpolarized PD by 6 +/- 1 mV (n = 13). The nucleotides UTP, ATP and ITP (10 mumol/l) depolarized PD by 12 +/- 1 mV (n = 7), 8 +/- 1 mV (n = 65) and 5 +/- 1 mV (n = 6) respectively. GTP, [alpha, beta-methylene]ATP and adenosine had no significant effect.(ABSTRACT TRUNCATED AT 250 WORDS)