IN VITRO CORTICOSTEROID BIOSYNTHESIS IN ADRENALS OF RATS URAEMIC AFTER BILATERAL NEPHRECTOMY
ABSTRACT After bilateral nephrectomy, adrenal sections of uraemic rats were incubated in Krebs-Ringer bicarbonate glucose solution. The in vitro production of 18-OH-corticosterone, aldosterone, 18-OH-deoxycorticosterone and corticosterone from 4-14C-progesterone, 1,2-3H-deoxycorticosterone and the in vitro production of aldosterone and corticosterone from endogenous precursors were investigated. The biosynthesis of corticosterone from endogenous precursors was diminished, while the percentage conversion of labelled progesterone and deoxycorticosterone to corticosterone remained unchanged. Aldosterone production from endogenous precursors was not reduced and the incorporation of precursor radioactivity into aldosterone, 18-OH-corticosterone and 18-OH-deoxycorticosterone was increased. It was concluded that in the rat, aldosterone biosynthesis can also be maintained in the absence of the renin angiotensin system and that metabolic changes, possibly hyperpotassaemia or a decrease in the Na/K ratio, may have caused a specific activation of C18-hydroxylating enzymes.