Ca2+ uptake by endoplasmic reticulum of renal cortex. I. Ionic requirements and regulation in vitro.
A subcellular fraction enriched in cytochrome c reductase (7.9-fold) and relatively de-enriched (0.64-fold) in Na+/K(+)-ATPase was prepared from canine kidney cortex by sucrose density gradient ultracentrifugation. It was shown by electron microscopy to consist primarily of a light fraction of endoplasmic reticulum (LER). LER vesicles displayed ATP-dependent 45Ca2+ uptake that was insensitive to 10 mM KCN or NaN3, and was promptly released by 20 microM A23187 or ionomycin. Inositol-1,4,5-trisphosphate (IP3) appeared to produce a time-dependent release of 45Ca2+. Vanadate inhibited 45Ca2+ uptake with a Ki approximately 0.3 mM, further suggesting that the activity resided in the ER rather than the plasma membrane. 45Ca2+ uptake by LER, at 5 microM total [Ca2+], displayed a strong dependence on divalent cations (Mg2+ greater than Co2+ greater than Mn2+ much greater than Ba2+ greater than or equal to Cd2+ greater than or equal to Sr2+, present at 2 mM) as well as on monovalent cations (Na+ greater than or equal to K+ + Na+ greater than K+ greater than Li+ greater than choline +), and anions (Cl- greater than acetate- greater than or equal to NO3- greater than or equal to F- greater than H2PO4- much greater than gluconate- greater than or equal to oxalate= much greater than SO4=). It had a fairly narrow pH optimum (7.25-7.50). Preincubation (10 min) of LER vesicles with 12-O-tetradecanoylphorbol-13-acetate (TPA) stimulated LER Ca2+ uptake; this effect was enhanced in the presence of renal cytosol [5% (vol/vol)].(ABSTRACT TRUNCATED AT 250 WORDS)
Moskowitz
D W
DW
Department of Medicine, St. Louis University School of Medicine, John Cochran VA Medical Center, MO 63106.
Hruska
K A
KA
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002117:Calcitriol / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D002147:Calmodulin / Q000494:pharmacology; D002413:Cations, Divalent / Q000494:pharmacology*; D003035:Cobalt / Q000494:pharmacology; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D005260:Female; D006863:Hydrogen-Ion Concentration; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007672:Kidney Cortex / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008345:Manganese / Q000494:pharmacology; D008854:Microscopy, Electron; D013347:Subcellular Fractions / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014461:Ultracentrifugation
D002132:Calcium Radioisotopes; D002147:Calmodulin; D002413:Cations, Divalent; D001464:Barium; D000001:Calcimycin; D003035:Cobalt; D008345:Manganese; D015759:Ionomycin; D003994:Bucladesine; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D002117:Calcitriol; D008274:Magnesium; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium