The factors that establish and maintain adrenocortical zonation and proliferation are poorly understood but include the pituitary hormone adrenocorticotrophin (ACTH), angiotensin II and potassium. To examine this capsular gland preparations largely glomerulosa (zg) with some fasciculata (zf), were cultured in vitro in Eagles MEM (3.6mM K+) for 1, 4 and 8 days and exposed these treatments. Rat zona glomerulosa proliferative activity, as judged by the rate of DNA synthesis, was determined by FACS analysis and immunocytochemistry through incorporation of the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU, 20 mg/ml). Mitogenic activity and cellular function over this period were assessed by expression and phosphorylation of the extracellular signal regulated kinases (ERKs) and aldosterone synthesis respectively.
Angiotensin II (100nm), ACTH (1nM) and potassium (8.4mM) caused an increase in DNA synthesis after 24hours which appeared evenly distributed throughout the zona glomerulosa, in contrast to control tissues in which proliferative activity was only visualised in the cells lying immediately beneath the connective tissue capsule. This was accompanied by a highly significant increase in aldosterone production over this period (P<0.01). After 4 days only ACTH and AngII were shown to further increase DNA synthesis, with a significant rise in aldosterone production seen only in AngII treated tissues (P<0.05). After 1,4 and 8 days in culture AngII and ACTH both up regulated total ERK expression compared to control, but 8.4mM potassium did not. None of the treatments initiated ERK phosphorylation after these time periods.
This data suggests that angII, ACTH and potassium stimulate steroid production and cellular proliferation in adrenal capsular preparations in vitro. Furthermore, The glomerulosa wide distribution of BrdU incorporation caused by these treatments, contrasting with its limitation to the subcapsular layer in controls, suggests that the whole glomerulosa has the potential to function as a stem cell population in this tissue.
08 - 11 Apr 2002
British Endocrine Societies