Effects of sodium selenite on vascular smooth muscle reactivity

The effects of sodium selenite (Na2SeO3) on the vascular smooth muscle reactivity of rabbit aorta were studied. In isolated rabbit aorta, Na2SeO3 inhibited contractile response to phenylephrine and developed a lasting contracture in the vascular tissue. Relaxation in phenylephrine-precontracted aortic rings induced by sodium nitroprusside and 8-bromoguanosine 3':5'-cyclic-monophosphate was also inhibited. Preliminary data obtained with ascorbic acid suggested a partial involvement of an oxidative mechanism. Excluding the possibility that Se damages actin or modifies its distribution (immunohistochemical evaluation), results indicate that Se alters vascular smooth muscle reactivity by inhibiting both its contracting and relaxing properties. Calcium-dependent mechanisms appear to be primarily involved and an interference with calcium re-uptake by sarcoplasmic reticulum as a possible site of Se vascular action could be hypothesized. (C) 2000 Academic Press.