Heparin inhibits the inositol 1,4,5-trisphosphate-dependent, but not the independent, calcium release induced by guanine nucleotide in vascular smooth muscle.
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.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology*; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000502:physiology*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D011343:Procaine / Q000494:pharmacology; D011817:Rabbits; D013403:Sugar Phosphates / Q000502:physiology*; D013873:Thionucleotides / Q000494:pharmacology
D007295:Inositol Phosphates; D013403:Sugar Phosphates; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002110:Caffeine; D011343:Procaine; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D006493:Heparin; D019204:GTP-Binding Proteins; D002118:Calcium