Effect of osmolarity on aldosterone production by rat adrenal glomerulosa cells.
The effect of osmotic changes on aldosterone production, [Ca2+]i and voltage-gated Ca2+ currents, was studied in cultured rat glomerulosa cells. Alteration of osmolarity by sucrose addition in the 250-330 mosM range did not influence aldosterone production per se, but it substantially affected K+-stimulated aldosterone production. Hyposmosis markedly increased the hormone response evoked by raising [K+] from 3.6 to 5 mM, whereas hyperosmosis had a mild decreasing effect. Cytoplasmic [Ca2+]i, measured in single glomerulosa cells, did not show detectable change in response to either hyposmotic or hyperosmotic exposure, but the [Ca2+]i signal evoked by elevation of [K+] to 5 mM was augmented in hyposmotic solution. The osmosensitivity of the transient (T)-type and long-lasting (L)-type voltage-gated Ca2+ currents was studied using the nystatin-perforated voltage-clamp technique. Lowering osmolarity to 250 mosM significantly increased the amplitude of the T-type current, and it had a transient augmenting effect on L-type current amplitude. Hyperosmotic solution (330 mosM) reduced L-type current amplitude but did not evoke significant change in T-type current. These results indicate that the responsiveness of rat glomerulosa cells to physiological elevation of [K+] is remarkably influenced by changes in osmolarity by means of modulating the function of voltage-gated Ca2+ channels.
Makara
J K
JK
Department of Physiology, Semmelweis University Medical School, Budapest, Hungary.
Petheö
G L
GL
Tóth
A
A
Spät
A
A
D000450:Aldosterone / Q000096:biosynthesis*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D009994:Osmolar Concentration; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015384:Zona Glomerulosa / Q000378:metabolism*
D015220:Calcium Channels; D015221:Potassium Channels; D000450:Aldosterone; D002118:Calcium