Corticosteroidogenesis and cytochrome levels in the regenerating rat adrenal

Homogenate preparations from the regenerating rat adrenal have reduced 11β-hydroxylating activity. To further examine this finding, mitochondria from control and regenerating rat adrenals have been isolated 3, 5, and 8 weeks following adrenal enucleation. The levels of cytochrome P-450 and the normal respiratory chain cytochromes were measured in addition to the ability of these mitochondrial preparations to carry out steroid hydroxylations. After 3 and 5 weeks of regeneration cytochrome P-450 levels were 55 and 78%, respectively, of control levels while after 8 weeks the levels were comparable in both groups. Similar results were obtained for microsomal cytochrome P-450. For all time periods studied, regenerating adrenal mitochondrial 11β-hydroxylase activity was low when malate or malate plus NADP were sources of reducing equivalents. With NADPH, however, corticosterone production was normal. These findings suggest that decreased NADPH generation may be the major factor involved in the reduced 11β-hydroxylating activity of the regenerating rat adrenal.