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Platelet‐activating factor increases inositol phosphate production and cytosolic free Ca 2+ concentrations in cultured rat Kupffer cells
Author(s) -
Fisher Rory A.,
Sharma Ram V.,
Bhalla Ramesh C.
Publication year - 1989
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(89)81421-8
Subject(s) - platelet activating factor , glycogenolysis , inositol phosphate , endocrinology , medicine , inositol , kupffer cell , cytosol , receptor , protein kinase c , chemistry , biology , biochemistry , phosphorylation , metabolism , enzyme
Platelet‐activating factor (PAF) stimulates glycogenolysis in perfused livers but not in isolated hepatocytes [(1984) J. Biol. Chem. 259, 8685–8688]. PAF‐induced glycogenolysis in liver is associated closely with a pronounced constriction of the hepatic vasculature [(1986) J. Biol. Chem. 261, 644–649]. These and other observations suggest that PAF stimulates glycogenolysis in liver indirectly by interactions with cells other than hepatocytes. We have evaluated effects of PAF on hepatic Kupffer cells, which regulate flow through the hepatic sinusoids. Application of PAF to [ 3 H]inositol‐labeled Kupffer cells produced dose‐dependent increases in [ 3 H]inositol phosphates with an EC 50 value of 4 × 10 −10 M. Increasesin inositol phosphate production in response to PAF were inhibited by a specific PAF receptor antagonist, SRI 63‐675 (2 × 10 −7 M), and stimulus of protein kinase C, phorbol 12‐myristate 13‐acetate (1 × 10 −7 M). Measurements of cytosolic free Ca 2+ concentrations ([Ca 2+ ] i ) in single Kupffer cells loaded with Fura‐2 demonstrated that application of PAF (2 × 10 −9 M) resulted in significant increases in [Ca 2+ ] i . These observations lead us to propose that interactions of PAF with Kupffer cells may result in the hemodynamic and metabolic responses to PAF in liver.