The role of tyrosine kinases in capacitative calcium influx-mediated aldosterone production in bovine adrenal zona glomerulosa cells.
In adrenal glomerulosa cells, the stimulation of aldosterone biosynthesis by angiotensin II (Ang II) involves the activation of a capacitative Ca(2+) influx through calcium release-activated calcium (CRAC) channels. In various mammalian cell systems, it has been shown that CRAC channel activation and Ca(2+) entry require tyrosine kinase activity. We have therefore examined in this work whether similar mechanisms contribute to Ang II-induced mineralocorticoid biosynthesis. In fluo-3-loaded isolated bovine glomerulosa cells, two inhibitors of tyrosine kinases, genistein and methyl-2, 5-dihydroxycinnamate (MDHC) (100 microM) prevented capacitative Ca(2+) entry elicited by Ang II (by 54 and 62% respectively), while the inhibitor of epidermal growth factor (EGF) receptor tyrosine kinase, lavendustin A, was without effect. Similar results were observed on Ca(2+) influx triggered by thapsigargin, an inhibitor of microsomal Ca(2+) pumps. The inhibitors blocked Ang II-stimulated pregnenolone and aldosterone production in the same rank order. In addition to its specific effect on capacitative Ca(2+) influx, genistein also affected the late steps of the steroidogenic pathway, as shown by experiments in which the rate-limiting step (intramitochondrial cholesterol transfer) was bypassed with 25-OH-cholesterol (25-OH-Chol), cytosolic calcium was clamped at stimulated levels or precursors of the late enzymatic steps were supplied. In contrast, genistin, a structural analogue of genistein devoid of tyrosine kinase inhibitory activity, was almost without effect on pregnenolone or 11-deoxycorticosterone (DOC) conversion to aldosterone. These results suggest that, in bovine adrenal glomerulosa cells, Ang II promotes capacitative Ca(2+) influx and aldosterone biosynthesis through tyrosine kinase activation.
Aptel
H B
HB
Division of Endocrinology and Diabetology, Department of Internal Medicine, University Hospital, CH-1211 Geneva 14, Switzerland.
Burnay
M M
MM
Rossier
M F
MF
Capponi
A M
AM
D000450:Aldosterone / Q000096:biosynthesis*; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002417:Cattle; D002478:Cells, Cultured; D002934:Cinnamates / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000187:drug effects; D019833:Genistein / Q000494:pharmacology; D010636:Phenols / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D015384:Zona Glomerulosa / Q000187:drug effects / Q000378:metabolism*
D002121:Calcium Channel Blockers; D002934:Cinnamates; D004791:Enzyme Inhibitors; D010636:Phenols; D019837:Ryanodine Receptor Calcium Release Channel; D000804:Angiotensin II; C062898:lavendustin A; D000450:Aldosterone; C067472:methyl 2,5-dihydroxycinnamate; D019284:Thapsigargin; D019833:Genistein; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D002118:Calcium