Effect of parathyroid hormone on acid/base transport in rabbit renal proximal tubule S3 segment.
The effect of parathyroid hormone (PTH) on acid/base transport in isolated rabbit renal proximal tubule S3 segment was investigated with double-barreled and conventional microelectrodes. PTH (10 nM) induced a small depolarization and enhanced the initial rates of cell pH (pHi) increase and cell Cl- ([Cl-]i) decrease in response to bath Cl- removal by 28.0 +/- 2.1% and 31.0 +/- 6.4% respectively. The calculated initial HCO3- influx to bath Cl- removal was also enhanced by 28%. On the other hand, PTH reduced the initial rate of pHi decrease to luminal Na+ removal in the absence of HCO3-/CO2 by 20.4 +/- 3.9%. The PTH-induced depolarization was not accompanied with changes in steady-state pHi or [Cl-]i levels, but was greatly attenuated in the presence of ouabain (0.1 mM). Either dibutyryl-cAMP (0.1 mM) plus theophylline (1 mM) or forskolin (10 microM) alone could reproduce all the effects of PTH. These results indicate that (a) PTH inhibits the luminal Na+/H+ exchanger but stimulates the basolateral Cl-/HCO3- exchanger in the S3 segment; (b) the PTH-induced depolarization largely results from inhibition of Na+/K(+)-ATPase and (c) all these effects are at least partly mediated by a cAMP-dependent mechanism.
First Department of Internal Medicine, Tokyo University School of Medicine, Japan.
G
G
Seki
S
S
Taniguchi
S
S
Uwatoko
K
K
Suzuki
K
K
Kurokawa
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D005260:Female; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects; D010042:Ouabain / Q000494:pharmacology; D010281:Parathyroid Hormone / Q000494:pharmacology*; D011817:Rabbits; D017923:Sodium-Hydrogen Exchangers; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D013806:Theophylline / Q000494:pharmacology
D001639:Bicarbonates; D002352:Carrier Proteins; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; D010281:Parathyroid Hormone; D017923:Sodium-Hydrogen Exchangers; D005576:Colforsin; D010042:Ouabain; D003994:Bucladesine; D013806:Theophylline; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase