PHENOTYPIC CHANGES AND PROLIFERATION OF ADRENOCORTICAL-CELLS DURING ADRENAL REGENERATION IN RATS

Adrenal regeneration after enucleation includes both cell proliferatio n and differentiation, but the phenotype of the proliferating cell rem ains controversial. Immunoperoxidase localization of cytochrome P450 a ldosterone synthase (P450aldo) and cytochrome P450 11 beta-hydroxylase (P45011 beta) and of Ki-67 was used to identify adrenocortical cell p henotypes and proliferating cells; respectively. Comparisons were made between regenerating and intact adrenals collected from rats on low o r normal Na+ diets. During the first week after enucleation, P45011 be ta was expressed reflecting the presence of fasciculata cells; however , P450aldo was detected only in adrenals from low Na+ rats. On normal and low Na+, glomerulosa cells were replaced by intermedia cells, wher eas on low Na+, glomerulosa cells were replaced by fasciculata cells. Proliferation was observed only in glomerulosa and fasciculata, but no t intermedia cells. These findings suggest that the expression of the glomerulosa cell phenotype is decreased in the early stages of adrenal regeneration, that differentiation from a glomerulosa to an intermedi ate or fasciculata cell phenotype is influenced by low Na+ and that gl omerulosa and fasciculata cells proliferate in response to enucleation .