Effects of two different experimental situations of hypothyroidism on serum aldosterone concentration and plasma renin in rats

Abstract

When hypothyroidism is induced surgically in early steps of development in the rat, an increase in serum aldosterone concentration (AC), in absence of changes in plasma renin activity (PRA), is observed.In contrast, in propylthiouracil (PTU) induced hypothyroidism, in adult animals, both AC and PRA decrease.Potassium iodide (KI) or triiodo-L-thyronine (T3) administration to thyroidectomized rats restores AC to normal levels, increasing PRA during the latter treatment.A close relationship between AC and plasma renin concentration (PRC) is observed in these experimental situations.The decrease in urinary aldosterone concentration (ACu), and the relation found between AC/ACu ratio and T3 concentration, suggest that metabolic clearance of aldosterone might be related to peripheric T3 levels in thyroidectomized animals, treated with KI or T3.These observations support the hypothesis, previously reported, which suggests different mechanisms involved in the control of aldosterone and renin release during the two different types of hypothyroidism.