Effects of Ions, Ouabain, Epinephrine, and Tetrodotoxin on Glucose Metabolism and on Contractility in the Perfused Guinea Pig Heart
- 1 June 1972
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Physiology and Pharmacology
- Vol. 50 (6) , 584-593
- https://doi.org/10.1139/y72-087
Abstract
In the perfused guinea pig heart, the rate of glucose-U-14C oxidation to 14CO2 was directly related to the external ratio [Ca2+]/[Na+]2. The metabolic stimulatory effects of ouabain were concentration-dependent, and those brought about by epinephrine were not prevented by the presence of ouabain or added Ca2+. The increased glucose utilization produced by ouabain or Ca2+ was reduced by tetrodotoxin (TTX), whereas that produced by epinephrine or reduced extracellular Na+ (100 mM) was not. It was also found that TTX inhibited the positive inotropic effects of Ca2+ and ouabain, but did not reduce the contractile force during perfusion in presence of epinephrine or at 100 mM Na+. It is concluded that (a) ouabain (or Ca2+) and epinephrine, producing additive effects, have different modes of action; (b) TTX and ouabain (or Ca2+) have antagonistic effects, probably resulting from their opposite action on calcium movements.Keywords
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