title: Effects of cationic modification on 45Ca uptake and insulin release by transplantable rat insulinoma cells maintained in tissue culture.
abstract: 1. Acute effects of cations on 45Ca uptake and insulin release by transplantable rat insulinoma cells were examined after 2-3 days culture in RPMI-1640 containing 11.1 mM glucose. 2. At 2.6 mM Ca2+, rat insulinoma cells (greater than 95% viability) released 78-158 ng insulin/10(6) cells during 60 min incubation with uptake at 2.19-3.24 nmol 45Ca/10(6) cells. 3. Addition of 2 mM La3+, Co2+, Mn2+, Zn2+ or Ba2+ did not affect 45Ca uptake. Insulin release was also unaffected by these cations with the exception of 87% inhibition in the presence of La3+ or Zn2+. 4. Omission of 5.9 mM K+, 1.2 mM Mg2+, 115 mM Na+ or H+ (pH 8.5) did not affect 45Ca uptake or insulin release, irrespective of osmotic compensation using choline chloride or sucrose. Rat insulinoma cells were similarly unresponsive to addition of 30.9 mM K+, 12 mM Mg2+ or H+ (pH 6.3). 5. Omission of 2.6 mM Ca2+ (with or without addition of 1 mM EGTA) or addition of 20.5 mM Ca2+ did not affect insulin release. 6. The results indicate that rat insulinoma cells are little affected by cationic modifications which have profound effects on Ca2+ handling and insulin release by pancreatic beta-cells. Dysregulation of insulin release by insulinoma cells is associated with marked irregularities in the control of transmembrane Ca2+ fluxes and sensitivity to extracellular Ca2+.
authors.affiliation: Department of Biochemistry, University of Surrey, Guildford, U.K.
authors.forename: S K
authors.initials: SK
authors.lastname: Swanston-Flatt
authors.forename: P R
authors.initials: PR
authors.lastname: Flatt
mesh_terms: D007516:Adenoma, Islet Cell / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002412:Cations / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007340:Insulinoma / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism
chemical_list: D002412:Cations; D007328:Insulin; D002118:Calcium