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[Ca 2+ ] i ‐ and insulin‐stimulating effect of the non‐membranepermeable phosphatase‐inhibitor microcystin‐LR in intact insulin‐secreting cells (RINm5F)
Author(s) -
Leiers T,
Bihlmayer A,
Ammon H P T,
Wahl M A
Publication year - 2000
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703441
Subject(s) - insulin , phosphatase , microcystin , medicine , endocrinology , chemistry , biochemistry , biology , enzyme , cyanobacteria , genetics , bacteria
Microcystin‐LR, a specific and effective inhibitor of serine/threonine phosphatases type 1/2A which does not permeate cells, was used to distinguish intracellular and extracellular effects of phosphatase inhibitors on insulin secretion by RINm5F cells. Incubation of intact RINm5F cells with microcystin‐LR (0.1–2 μ M ) almost doubled basal insulin release at 3 m M glucose but left maximal insulin release induced by KCl (30 m M ) unaffected. In parallel, there was an increase in cytosolic Ca 2+ by up to half maximum, which could be suppressed by the Ca 2+ ‐channel blocker D600. In contrast, microcystin‐LR incubation of intact cells did not affect phosphatase activity but significantly reduced phosphatase activity when used in cellular fractions. From these data we conclude that microcystin‐LR could affect Ca 2+ ‐channels and insulin release by inhibiting an extracellular phosphatase‐like activity.British Journal of Pharmacology (2000) 130 , 1406–1410; doi: 10.1038/sj.bjp.0703441