Effect of ionomycin on cell pH in isolated renal proximal tubules.
In isolated rabbit proximal tubules the addition of 2.0 microM but not 0.2 microM ionomycin induced a sustained increase in cell pH ([pH]i). This [pH]i response to 2.0 microM ionomycin was shown to be independent of several transporters such as Na+/H+ exchanger, Na(+)-HCO3- cotransporter, Cl-/HCO3- exchanger, or H(+)-ATPase. On the other hand, the removal of extracellular Ca2+ abolished the [pH]i increase or even induced a transient [pH]i decrease in the presence of ionomycin. These results are consistent with the induction of Ca2+/H+ exchange by ionomycin. Therefore Ca2+ ionophores should be used with caution as probes to estimate renal tubule functions.
Yamada
H
H
First Department of Internal Medicine, Tokyo University School of Medicine, Japan.
Seki
G
G
Taniguchi
S
S
Uwatoko
S
S
Suzuki
K
K
Kurokawa
K
K
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D015759:Ionomycin / Q000494:pharmacology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011817:Rabbits; D013997:Time Factors
D001639:Bicarbonates; D002352:Carrier Proteins; D015759:Ionomycin; D006180:Proton-Translocating ATPases; D002118:Calcium