A Cl- channel activated by parathyroid hormone in rabbit renal proximal tubule cells.
Previous data suggested an active Cl- conductance in the renal proximal convoluted tubule, although single channel conductance and regulation were not found. We have investigated the presence and regulation of the Cl- channel in proximal convoluted tubules by patch clamp analysis. The current-voltage relationship of whole cells with 130 mM NaCl in the pipette was nonlinear. The addition of 1-34 PTH (10(-8) M), forskolin, or cAMP significantly increased whole cell Cl- conductance. We found a single Cl- channel in excised apical membranes possessing conductance of 33 picosiemens (pS) at positive and 22.5 pS at negative potential, which was blocked by 4,4'-diisothiocyanostilbene-2,2'- disulfonic acid (10(-4) M) and was selective to Cl- (Cl/Na = 10). The channel was activated by prolonged membrane depolarization, by a catalytic subunit of protein kinase A (PKA), or by purified kinase C (PKC), but not by Ca2+ (1 microM) inside the membrane. During cell-attached patch clamping, the channel was similarly activated by PTH, phorbol ester, or dibutyryl cAMP in a dose-dependent manner. To investigate second messenger contributions to the PTH-action, the PTH-evoked channels were modified further by the subsequent addition of several blockers of the second messengers. This suggested that PKA and PKC were involved in Cl- channel activation. We therefore conclude that renal proximal convoluted tubule cells possess an apical Cl- channel activated by PTH via the PKA and PKC pathways.
Suzuki
M
M
Second Department of Internal Medicine, Jikei University, Tokyo, Japan.
Morita
T
T
Hanaoka
K
K
Kawaguchi
Y
Y
Sakai
O
O
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects* / Q000502:physiology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011493:Protein Kinase C / Q000502:physiology; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D010281:Parathyroid Hormone; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium