As recently was shown ionising gamma-irradiation evokes arterial hypertension. The mechanisms responsible for its development can involve abnormalities in both vascular smooth muscle and endothelium activity.

The goal of the present study was to investigate the influence of ionising irradiation on outward large conductance Ca2+ -activated K+ (BKCa) current in vascular smooth muscle and endothelial cells and possible role of this current in irradiation-induced vasospasm development.

Experiments were made using current-clamp method in whole-cell configuration on fresh isolated rat aorta smooth muscle cells (SMC) and secondary cultured rat coronary arteries endotheliocytes (EC).

It was shown that summary outward K+ current in SMC obtained from animals on 9th and 30th days after whole body gamma-irradiation (Co60, 6 Gy) significantly decreased as compared with SMC from control animals and this effect is more expressed on 30th day after radiation influence. The potent selective inhibitor of BKCa current, paxilline (5x10-7 M), significantly decreased summary outward K+ current in control SMC but had not affect on this current in SMC from irradiated rat aorta. Similarly, in EC from gamma-irradiated tissues (obtained on 9th day after irradiation) summary outward K+ current and its paxilline-sensitive component both were depressed in compared with K+ currents in control animals EC.

Therefore, our data suggest that BKCa current is decreased in vascular SMC and EC and it may contribute to development of elicited by ionising irradiation vasospasm and arterial hypertension.