Stimulation by cyclic GMP of sodium efflux in barnacle muscle fibres

The Journal of Physiology
E E Bittar, D M Sharp


1. The ouabain-insensitive Na efflux in barnacle muscle fibres is promptly stimulated by injection of cyclic GMP. The minimal effective injected concentration is found to be about 10(-7) M. This effect of cyclic GMP could not be mimicked by injecting 5'-GMP. 2. External application of ouabain (10(-4) M) to fibres not pretreated with ouabain during the stimulatory response to cyclic GMP causes some inhibition of the Na efflux indicating that cyclic GMP does not cause appreciable inhibition of the Na:K pump. 3. The magnitude of the stimulatory response to injected cyclic GMP depends on the external Ca2+ concentration, as well as pHe but not on the Na+, K+ or Mg2+ concentration. It also depends on pHi, since acidification of HCO3-containing ASW leads to a greater enhancement of the response to cyclic GMP than is observed with acidified HERPES-ASW. 4. Stabilization of myoplasmic pCa by injecting 100 mM-EGTA before or after cyclic GMP fails to alter the magnitude of the response to the nucleotide. Enrichment of the fibre with Mg2+ at the time of injection of cyclic GMP leads to a reduced response. No change in response, however, is seen when the internal free Mg concentration is suddenly reduced by injecting 0.05 M-pyrophosphate wit...Continue Reading


Feb 28, 1981·The Journal of Membrane Biology·D Mason-Sharp, E E Bittar
Jan 1, 1987·Comparative Biochemistry and Physiology. B, Comparative Biochemistry·E E Bittar, P R Girard
Jan 1, 1990·Toxicology and Applied Pharmacology·E E BittarY P Huang
May 1, 1987·The American Journal of Physiology·H MatsuokaH Matsuo

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