The specific GTP requirement for inositol 1,4,5-trisphosphate-induced Ca2+ release from skinned vascular smooth muscle.
Exogenous GTP was required for the induction of Ca2+ release from smooth muscle SR by IP3 if endogenous GTP was depleted. NaN3 could function as a partial substitute for GTP as a cofactor for the IP3-induced Ca2+ release from the SR. In contrast to the IP3-induced Ca2+ release, caffeine-induced Ca2+ release from the SR did not require GTP. Pertussis toxin inhibited the IP3-induced Ca2+ release from the SR, whereas it had no effect on caffeine-induced Ca2+ release. These results indicate that in smooth muscle two different Ca2+ release-channels exist in the SR: (a) activated by IP3, and (b) activated by caffeine or Ca2+.
Saida
K
K
Department of Pharmacology, University of Miami, School of Medicine, FL 33101.
Twort
C
C
van Breemen
C
C
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002478:Cells, Cultured; D006160:Guanosine Triphosphate / Q000378:metabolism*; D066298:In Vitro Techniques; D007292:Inosine Nucleotides / Q000494:pharmacology*; D007293:Inosine Triphosphate / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000502:physiology; D037342:Pertussis Toxin; D011817:Rabbits; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D002132:Calcium Radioisotopes; D007292:Inosine Nucleotides; D010566:Virulence Factors, Bordetella; D007293:Inosine Triphosphate; D002110:Caffeine; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D002118:Calcium