PERMISSIVE ROLE OF ALPHA-TOCOPHEROL IN THE STIMULATION OF ALDOSTERONEBY SODIUM DEPLETION IN THE GUINEA-PIG

To investigate the role of vitamin E in aldosterone synthesis, in vivo and in vitro studies were done in alpha-tocopherol-depleted guinea pi gs. Seventy-one days of low vitamin E intake (< 5 mg/kg feed) reduced the concentration of alpha-tocopherol in serum, liver and adrenals to low levels with no signs of hypovitaminosis. Aldosterone secretion was stimulated by 15 days on a low sodium diet (200 mg/kg feed) in contro ls and vitamin E-depleted animals. Sodium depletion in controls stimul ated plasma aldosterone by 335%, Vitamin E depletion reduced the stimu lation of plasma aldosterone to only 112% (p < 0.05), In vitro aldoste rone secretion by adrenal cells from sodium-depleted animals was 252% higher than secretion by cells from controls. This enhancement of in v itro aldosterone secretion following in vice sodium depletion was abol ished completely by combined in vivo vitamin E and sodium depletion (p < 0.05). No significant differences between groups were found for pla sma renin activity, adrenocorticotrophin and serum potassium, suggesti ng that intra-adrenal mechanisms like damage by enhanced lipid peroxid ation in alpha-tocopherol-depleted animals rather than changes in humo ral aldosterone-regulating factors are the cause of the attenuated ald osterone response to sodium depletion.