Reversible blockade of the calcium-activated nonselective cation channel in brown fat cells by the sulfhydryl reagents mercury and thimerosal.
We have used patch-clamp techniques to study the effect of the sulfhydryl group oxidizing agents mercury and thimerosal on calcium-activated nonselective cation channels from brown adipose tissue. 100 nmol/l mercury and 50 mumol/l thimerosal induced a complete block. Blockade could be reversed by reduction of the mercaptide by dithiotreitol (DTT). Mercury was found to be the most potent blocker (IC50-value 21 x 10(-9) mol/l), whereas thimerosal (IC50-value 1.5 x 10(-6) mol/l) was as effective as 3',5-dichlorodiphenylamine-2-carboxylic acid (DCDPC). The DCDPC effect, however, could not be reversed by DTT, indicating different blocking mechanisms. It is concluded that SH-groups are involved in gating of the calcium-activated nonselective channel.
Koivisto
A
A
Wenner-Gren Institute, Arrhenius Laboratories F3, Stockholm University, Sweden.
Siemen
D
D
Nedergaard
J
J
D002001:Adipose Tissue, Brown / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002412:Cations / Q000378:metabolism*; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D008628:Mercury / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology*
D002412:Cations; D007473:Ion Channels; D013439:Sulfhydryl Reagents; D013849:Thimerosal; D008628:Mercury; D002118:Calcium