OBJECTIVETo investigate the changes of large conductance Ca(2+)-activated K(+) channel (BK channel) on coronary smooth muscle cells from diabetic rats.

METHODSStreptozotocin-induced rat diabetic animal model was used. Coronary smooth muscle cells were isolated by enzyme digestion. BK currents in control and diabetic groups were recorded by patch clamp technique in whole cell configuration, and BK channel protein expression was detected by Western blot. Calcium concentration was measured by fluorescence assay.

RESULTSCompared with control group, BK current densities in diabetic group were significantly decreased when test potentials > 100 mV (P < 0.05). BK current densities were (275 ± 40) pA/pF in control group (n = 8) and (70 ± 10) pA/pF in diabetic group (n = 6) at 150 mV test potentials. α-subunit protein expression was similar between the groups (P > 0.05), however, β1-subunit protein expression was significantly reduced in diabetic group than in control group (P < 0.05). Calcium concentrations were significantly increased in diabetic group control group (151 ± 18) nmol/L (n = 6) than in control group (92 ± 7) nmol/L (n = 5, P < 0.05).

CONCLUSIONObserved β1-subunit downregulation, BK current density decrease and cytosolic calcium concentration increase in smooth muscle cells of diabetic coronary arteries may be associated with coronary dysfunction in diabetic rats.