[Functional and molecular changes of large-conductance calcium-dependent potassium in rat aortic smooth muscle cells...

The effects of whole body gamma-irradiation on large conductance Ca(2+)-activated K+ channels (BK(Ca)) function and mRNA expression in rat thoracic aorta smooth muscle cells (SMCs) were studied using combined patch-clamp technique in whole-cell modification and RT-PCR analysis. The stimulation of control SMCs by increasingly depolarized voltage steps showed clearly expressed outward K+ currents in control SMCs. Outward currents in SMCs obtained from irradiated animals on the 9th and 30th days post-irradiation demonstrated a significant decrease of K current density amplitudes. Paxillin was without effect on irradiated cells on 30th day post-irradiation indicating the absence of conductance through BK(Ca) channels. The results of RT-PCR analysis showed that expression both alpha-subunit and beta1-subunit of BK(Ca) channels appears to be considerably diminished on 30th day post-irradiation. It is likely that radiation-induced malfunction functional activity of channels is related with insufficient expression of BK(Ca) structural elements in SMCs. In conclusion, the data obtained clearly demonstrate that decreased of the BK(Ca) channels alpha- and beta1-subunit expression in SMCs is a key factor of abnormality in BK(Ca) channels activity. This abnormality may contribute to vasorelaxing force depression following non-fatal whole-body gamma-irradiation.