Ca channels in adrenal glomerulosa cells: K+ and angiotensin II increase T-type Ca channel current.
Ca channel currents were studied in freshly dispersed bovine adrenal glomerulosa cells to better understand the control of aldosterone secretion by extracellular K concentration (Ko) and angiotensin II (AII). The whole-cell variation of the patch voltage clamp technique was used. Two types of Ca channels were found. One type is similar to the "T-type" Ca channels found in many excitable cells. These channels deactivate slowly (tau approximately equal to 7 ms at -75 mV) and inactivate rapidly during strong depolarizations. The second channel type activates and inactivates at more positive potentials than the T-type Ca channels and deactivates rapidly. These channels are similar to the "L-type" Ca channels found in muscle and nerve. Our studies provide three reasons for concluding that T-type Ca channels have an important role in mediating stimulus-secretion coupling in response to high K+ or AII: (i) aldosterone secretion and steady-state current through T-type Ca channels are biphasic functions of Ko and both increase in parallel for Ko = 2-10 mM; (ii) nitrendipine blocks the T-type Ca channels and the stimulation of aldosterone secretion by high K+ or AII with similar potency; (iii) AII increases Ca entry through the T-type Ca channels.
D000302:Adrenal Cortex / Q000166:cytology / Q000378:metabolism*; D000450:Aldosterone / Q000378:metabolism; D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D002417:Cattle; D007473:Ion Channels / Q000145:classification / Q000187:drug effects* / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D009568:Nitrendipine / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D007473:Ion Channels; D000804:Angiotensin II; D000450:Aldosterone; D009568:Nitrendipine; D011188:Potassium