Glucocorticoids stimulate rabbit proximal convoluted tubule acidification.
Glucocorticoids have an important role in renal acidification; however, a direct effect of glucocorticoids on proximal convoluted tubule (PCT) acidification has not been directly demonstrated. In the present in vitro microperfusion study PCT from animals receiving dexamethasone (600 micrograms/kg twice daily for 2 d and 2 h before killing) had a significantly higher rate of bicarbonate absorption than did controls (92.0 +/- 13.3 vs 59.9 +/- 3.2 pmol/mm.min, P < 0.01). To examine if glucocorticoids had a direct epithelial action, dexamethasone was added to the bath of PCT perfused in vitro. After 3 h of incubation in paired experiments 10(-6) M and 10(-5) M dexamethasone resulted in an approximately 30% stimulation in the rate of bicarbonate absorption. 10(-7) M dexamethasone and 10(-6) M aldosterone had no effect on bicarbonate absorption. The stimulation of acidification by 10(-5) M dexamethasone was blocked by actinomycin D and cycloheximide. These data are consistent with a direct effect of glucocorticoids on PCT acidification, and this effect is dependent upon protein synthesis.
Baum
M
M
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas 75235-9063.
Quigley
R
R
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000187:drug effects / Q000502:physiology*; D007679:Kidney Medulla / Q000187:drug effects / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D011817:Rabbits
D001639:Bicarbonates; D003609:Dactinomycin; D000450:Aldosterone; D003907:Dexamethasone; D003513:Cycloheximide