title: Introduction of antibody (PL/IM 430) to a 100 kDa protein into permeabilised platelets inhibits intracellular sequestration of Ca2+.
abstract: A monoclonal antibody (PL/IM 430), previously found to inhibit the uptake of Ca2+ into highly purified platelet intracellular membrane vesicles (Hack, N., Wilkinson, J.M. and Crawford, N. 1988, Biochem. J. 250, 355-361) has been introduced into saponin-permeabilised platelets. At a saponin concentration (20-25 micrograms/ml) commensurate with total LDH release, sequestration of Ca2+ into intracellular non-mitochondrial stores is inhibited by the antibody (approximately 50% inhibition at 20 micrograms/ml IgG). At higher saponin concentrations when intracellular binding of 125I-labelled mAb is maximum, inhibition of Ca2+ sequestration approaches 70%. The inhibition is specific, control studies with non-platelet directed mouse IgG and mAbs which immunoblot platelet antigens other than the 100 kDa protein did not affect the Ca2+ sequestration. No effect of the antibody were observed against IP3-induced release of prestored Ca2+, either in permeabilised platelets or with isolated intracellular membrane vesicles. The mAb PL/IM 430 appears to bind only to the Ca2+ translocating channel protein associated with the intracellular membrane (Ca2+ + Mg2+) ATPase and not to Ca2+ channels responsive to IP3.
authors.affiliation: Institute of Medical Sciences, University of Toronto, Canada.
authors.forename: N
authors.initials: N
authors.lastname: Hack
authors.forename: K S
authors.initials: KS
authors.lastname: Authi
authors.forename: N
authors.initials: N
authors.lastname: Crawford
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D001792:Blood Platelets / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism* / Q000493:pharmacokinetics; D015220:Calcium Channels / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D006801:Humans; D007457:Iodine Radioisotopes; D008565:Membrane Proteins / Q000276:immunology* / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D015220:Calcium Channels; D007457:Iodine Radioisotopes; D008565:Membrane Proteins; D010744:Phosphoric Monoester Hydrolases; C021822:myo-inositol-1 (or 4)-monophosphatase; D000252:Calcium-Transporting ATPases; D002118:Calcium