α1H T-type Ca2+ channel is the predominant subtype expressed in bovine and rat zona glomerulosa

Abstract

The low voltage-activated (T-type) Ca2+ channel has been implicated in the regulation of aldosterone secretion from the adrenal zona glomerulosa by extracellular K+ levels, angiotensin II, and ACTH. However, the identity of the specific subtype mediating this regulation has not been determined. We utilized in situ hybridization to examine the distribution of three newly cloned members of the T-type Ca2+ channel family, α1G, α1H, and α1I, in the rat and bovine adrenal gland. Substantial expression of only the mRNA transcript for the α1H-subunit was detected in the zona glomerulosa of both rat and bovine. A much weaker expression signal was detected for the α1H transcript in the zona fasciculata of bovine. Whole cell recordings of isolated bovine adrenal zona glomerulosa cells showed the native low voltage-activated current to be inhibited by NiCl2 with an IC50 of 6.4 ± 0.2 μM. Because the α1H subtype exhibits similar NiCl2 sensitivity, we propose that the α1Hsubtype is the predominant T-type Ca2+ channel present in the adrenal zona glomerulosa.