Uptake of calcium by pancreatic islet cell microsomes: inhibition by a monoclonal antibody to heart sarcoplasmic reticulum.
The uptake of Ca2+ by microsomes is thought to participate in the control of cytosolic Ca2+ activity in the insulin-producing pancreatic B-cell. In order to study such a phenomenon methods were developed to isolate microsomes from rat parotid cells, pancreatic islets and tumoral islet cells of the RINm5F line. In the latter case, a subcellular microsomal fraction was prepared in which the ratio of microsomal/mitochondrial enzyme markers, as well as that of ruthenium red-resistant/sensitive 45Ca2+ uptake was 20 times higher than in the corresponding mitochondrial subcellular fraction. The ATP-dependent net uptake of 45Ca2+ by RINm5F cell microsomes was inhibited at low temperature and by either vanadate or a monoclonal antibody to dog heart sarcoplasmic reticulum. Although the uptake of Ca2+ by microsomes may account for only a minor fraction of ATP consumption, its synarchistic regulation by ATP and Ca2+, at close-to-physiological concentrations, appeared well suited to play a major regulatory role in the control of cytosolic Ca2+ activity in intact islet cells.
Keenoy
M Y
MY
Laboratory of Experimental Medicine, Brussels University School of Medicine, Belgium.
Levitsky
D O
DO
Sener
A
A
Malaisse
W J
WJ
D000818:Animals; D000911:Antibodies, Monoclonal; D000968:Antimycin A / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000276:immunology*; D002460:Cell Line; D004285:Dogs; D007340:Insulinoma; D007515:Islets of Langerhans / Q000378:metabolism*; D007700:Kinetics; D008861:Microsomes / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology* / Q000276:immunology; D009840:Oligomycins / Q000494:pharmacology; D010190:Pancreatic Neoplasms; D010306:Parotid Gland / Q000378:metabolism; D051381:Rats; D012519:Sarcoplasmic Reticulum / Q000201:enzymology* / Q000276:immunology; D014638:Vanadates / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D009840:Oligomycins; D014638:Vanadates; D000968:Antimycin A; D000252:Calcium-Transporting ATPases; D002118:Calcium