ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract : We have isolated and characterized overlapping cDNAsencoding a novel, voltage-gated Ca2+ channel α1subunit, α1H, from a human medullary thyroid carcinoma cellline. The α1H subunit is structurally similar to previouslydescribed α1 subunits. Northern blot analysis indicates thatα1H mRNA is expressed throughout the brain, primarily in theamygdala, caudate nucleus, and putamen, as well as in several nonneuronaltissues, with relatively high levels in the liver, kidney, and heart.Ba2+ currents recorded from human embryonic kidney 293 cellstransiently expressing α1H activated at relativelyhyperpolarized potentials (-50 mV), rapidly inactivated (τ = 17 ms), andslowly deactivated. Similar results were observed in Xenopus oocytesexpressing α1H. Singlechannel measurements in human embryonickidney 293 cells revealed a single-channel conductance of ~9 pS. Thesechannels are blocked by Ni2+ (IC50 = 6.6 μM)and the T-type channel antagonists mibefradil (~50% block at 1 μM)and amiloride (IC50 = 167 μM). Thus,α1H-containing channels exhibit biophysical andpharmacological properties characteristic of low voltage-activated, or T-type,Ca2+ channels.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1471-4159.1999.0720791.x
Permalink