title: Negative inotropic effect of heparin on tension development in rat skinned skeletal muscle fibres.
abstract: Heparin inhibits inositol trisphosphate receptors, particularly in smooth muscle, but its effect on skeletal muscle is controversial. Our study showed that heparin induced a decrease in the amplitude of 10 mM caffeine-induced contracture in slow and fast saponin-skinned fibres. Moreover, measurements on Triton X-100-skinned fibres in soleus muscle showed that heparin alone decreased maximal Ca2(+)-activated tension and Ca2+ sensitivity of contractile proteins, whereas no significant effect was observed in extensor digitorum longus muscle. However, in the presence of caffeine, heparin decreased maximal Ca2(+)-activated tension in both muscles. It would appear that the heparin-induced decrease in the amplitude of caffeine contracture in rat skeletal muscle was not related to a direct inhibition of Ca2+ release from sarcoplasmic reticulum but to a desensitising effect of heparin and caffeine on myofilaments.
authors.affiliation: Laboratoire de Physiologie Générale, URA CNRS 1340, Faculté des Sciences et des Techniques, Nantes, France.
authors.forename: S
authors.initials: S
authors.lastname: Talon
authors.forename: C
authors.initials: C
authors.lastname: Huchet-Cadiou
authors.forename: C
authors.initials: C
authors.lastname: Léoty
mesh_terms: D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D003864:Depression, Chemical; D006493:Heparin / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism
chemical_list: D002110:Caffeine; D006493:Heparin; D002118:Calcium