Heparin inhibits the inositol 1,4,5-trisphosphate-dependent, but not the independent, calcium release induced by guanine nucleotide in vascular smooth muscle |
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Authors: | S Kobayashi A V Somlyo A P Somlyo |
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Affiliation: | Pennsylvania Muscle Institute, University of Pennsylvania School of Medicine, Philadelphia 19104-6083. |
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Abstract: | The effects of heparin on the release of intracellular Ca2+, assessed by tension development in saponin-permeabilized rabbit main pulmonary artery, were determined. Heparin inhibited (IC50 = 5 micrograms/ml) inositol 1,4,5-trisphosphate (InsP3)-induced, but not caffeine-induced, Ca2+ release. The initial (InsP3-dependent) component of GTP gamma S-induced Ca2+-release was also inhibited by heparin, but the InsP3-independent component was resistant to both heparin and procaine. These results support the existence of a G protein activated mechanism of Ca2+ release that is not mediated by InsP3 or by Ca2+-induced Ca2+ release. |
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