Electrophysiologic characteristics of the Ca-permeable channels, ECaC and CaT, in the kidney.
To investigate the molecular mechanism of Ca transport in the kidney, we have isolated Ca-permeable channels, rECaC (rat ECaC) and mCaT (mouse CaT1), from rodent kidney, which are recently reported as Ca-transporting proteins. RT-PCR suggested the presence of CaT1 in medullary tubules. It showed 67% homology with rECaC constructing a family. Whole cellular currents in Chinese hamster ovary (CHO) cells were measured by patch clamp. Expression of both proteins exhibited a similar large cation current, a high permeability to Ca, a time-dependent rapid inactivation, and a "run-down." When the pipet contained EGTA, the inactivation and the run-down did not occur. Addition of db-cAMP activated and following rp-cAMPS recovered the mCaT-induced current significantly, whereas no influence was observed in the rECaC-induced one. We conclude that ECaC and CaT are a molecular family of ion channel with similar characteristics, contributing Ca transport in the kidney.
Suzuki
M
M
Department of Pharmacology, Jichi Medical School, 3311-1, Yakushiji, Minamikawachi, Tochigi, 329-04, Japan. macsuz@jichi.ac.jp
Ishibashi
K
K
Ooki
G
G
Tsuruoka
S
S
Imai
M
M
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002463:Cell Membrane Permeability / Q000187:drug effects; D003001:Cloning, Molecular; D006224:Cricetinae; D000242:Cyclic AMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D050916:TRPV Cation Channels; D013873:Thionucleotides / Q000494:pharmacology; D014162:Transfection
D015220:Calcium Channels; D050916:TRPV Cation Channels; C492241:TRPV5 protein, rat; C120776:TRPV6 channel; D013873:Thionucleotides; C492240:Trpv5 protein, mouse; C016957:adenosine-3',5'-cyclic phosphorothioate; D004533:Egtazic Acid; D003994:Bucladesine; D000242:Cyclic AMP; D002118:Calcium