Effects of sodium selenite on vascular smooth muscle reactivity

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