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The specific GTP requirement for inositol 1,4,5-trisphosphate-induced Ca2+ release from skinned vascular smooth
K Saida1, C Twort, C van Breemen
1Department of Pharmacology, University of Miami, School of Medicine, FL 33101.
Journal of Cardiovascular Pharmacology
|January 1, 1988
Abstract:
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+.