Adaptation of rabbit cortical collecting duct to in vitro acid incubation.
Cortical collecting ducts (CCDs) isolated from acid-loaded rabbits and perfused in vitro absorb HCO3-, whereas CCDs from normal animals secrete HCO3-. We have previously shown that CCDs incubated in vitro for 3 h at pH 6.9 show a reduction in net (baseline and stimulated) HCO3- secretion. In this study we ascertained the minimum duration of an acidic stimulus necessary to induce adaptive changes in stimulated HCO3- secretion (determined in the absence of basolateral Cl-) and the roles of protein synthesis and cytoskeletal function in this process. CCDs incubated in acid (pH 6.8, HCO3- 6 mM) for 1 h followed by incubation at pH 7.4 (HCO3- 25 mM) for 2 h showed a 41% reduction in stimulated HCO3- secretion (P < 0.001), similar to that observed after 3 h of incubation at pH 6.8. However, this incubation protocol failed to enhance stimulated HCO3- absorption (determined in the absence of luminal Cl-). Addition of 10 microM anisomycin, a reversible inhibitor of protein synthesis, throughout the entire period of incubation (1 h at pH 6.8 plus 2 h at pH 7.4) blocked adaptive reduction in HCO3- secretion, as did exposure to anisomycin only during the initial 1 h of acid incubation. In contrast, anisomycin application during the 2-h incubation at pH 7.4 failed to block this adaptation of HCO3- secretion. Application of 4 microM actinomycin D, an inhibitor of DNA transcription, during the acid incubation also prevented the adaptive response, as did application during the total or during the 2-h pH 7.4 incubation period of 0.2 microM cytochalasin D, an inhibitor of actin filament function.(ABSTRACT TRUNCATED AT 250 WORDS)
Yasoshima
K
K
Department of Pediatrics, Albert Einstein College of Medicine, Bronx, New York 10461.
Satlin
L M
LM
Schwartz
G J
GJ
D000042:Absorption / Q000187:drug effects; D000143:Acids / Q000494:pharmacology*; D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D000841:Anisomycin / Q000494:pharmacology; D001639:Bicarbonates / Q000378:metabolism; D003470:Culture Media; D015638:Cytochalasin D / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000187:drug effects*; D011817:Rabbits
D000143:Acids; D001639:Bicarbonates; D003470:Culture Media; D003609:Dactinomycin; D015638:Cytochalasin D; D000841:Anisomycin