Ionizing irradiation increases vascular responsiveness and leads to arterial hypertension but these mechanisms remain unclear. We tested the hypnotizes that changes in the large conductance Ca²⁺-activated K⁺ channels (BK_Ca) activity in vascular smooth muscle cells (VSMCs) may contribute to irradiation-evoked arterial hypertension. BK_Ca play an essential role in vascular tone regulation via its involvement to the changes of VSMCs membrane potential with following changes in intracellular Ca²⁺ concentration. We also supposed that changes in BK_Ca activity under irradiation impact can be mediated by protein kinase C (PKC) which activity can be increased under action of irradiation. The study was performed on single isolated rat aorta VSMCs using patch-clamp techniques in standard whole-cell mode from healthy and single whole-body irradiated (source Co⁶⁰, dose 6 Gy) animals taken on 9^th (IR9) and 30^th day postirradiation (IR30), and anesthetized with sodium pentobarbital (50 mg/kg ip). Whole-cell outward K⁺ current in VSMCs from IR9 and IR30 at maximal value of depolarization step to -70 mV was significantly lower (33.21±1.67 pA/pF, n=11 and 18.22±2.51 pA/pF, n=12, respectively) as compared to control (63.21±4.7 pA/pF, n=10). In control VSMCs application of selective inhibitors of small conductance Ca²⁺-activated K⁺ channels (SK_Ca) apamin (1 μM), intermediate conductance Ca²⁺-activated K⁺ channels (IK_Ca,) charybdotoxin (1 μM), and BK_Ca paxilline (500 nM) leaded to decreasing of outward K⁺ current density to 39.41±0.61 pA/pF (n=5), 52.94±8.53 pA/pF (n=6), and 18.7±2.47 pA/pF (n=6) respectively, showing that in rat aorta VSMCs the main component of K⁺ current is BKCa current. Paxilline (500 nM) inhibited reduced K⁺ current in IR9 to 17.19±1.1 pA/pF (n=9) and had not effect on this current in IR30 aorta VSMCs (15.67±2.58 pA/pF, n=7)suggesting that on 30^th day postirradiation BK_Ca current eliminates completely. Potent PKC inhibitor chelerythrine (100 nM) slightly increased outward K⁺ current in VSMCs from healthy tissue to 90.87±4.92 pA/pF (n=6) and renewal K⁺ current reduced by action of ionizing irradiation in IR9 aorta VSMCs up to 89.4±3.78 pA/pF (n=9) and in IR30 tissue up to 74.4±5.98 pA/pF (n=6), suggesting that irradiation-evoked inhibition of BK_Ca current in aortic VSMCs is mediated by PKC. Taken together, these data indicate that ionizing irradiation leads to inhibition of outward K⁺ current in rat aorta VSMCs mainly via inhibition of BK_Ca current and this inhibition is mediated by PKC that may contribute to elevation of vascular tone under ionising irradiation impact and arterial hypertension development.