MgATP-dependent accumulation of calcium ions and inorganic phosphate in a liver reticular pool.
1. MgATP-dependent Ca2+ uptake by rat liver microsomal preparations and permeabilized hepatocytes was measured in the presence or absence of Pi. 2. Monitoring of free Ca2+ in incubation systems with a Ca2+ electrode in the presence of Pi (2-7 mM) revealed a biphasic Ca2+ uptake, with the onset of a second, Pi-dependent, Ca2+ accumulation. 3. Increasing Pi concentrations (up to 10 mM) caused a progressive enlargement of 45Ca2(+)-loading capacity of microsomal fractions. 4. As a result of Pi stimulation of active Ca2+ uptake, [32P]Pi and 45Ca2+ were co-accumulated. 5. Experiments with permeabilized hepatocytes revealed that the amount of Ca2+ releasable by myo-inositol 1,4,5-trisphosphate is unaffected by Pi.
Fulceri
R
R
Istituto di Patologia Generale, University of Siena, Italy.
Bellomo
G
G
Gamberucci
A
A
Benedetti
A
A
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002463:Cell Membrane Permeability; D002478:Cells, Cultured; D004072:Digitonin; D015544:Inositol 1,4,5-Trisphosphate / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D002132:Calcium Radioisotopes; D010710:Phosphates; D000001:Calcimycin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D004072:Digitonin; D002118:Calcium