Abstract
Summary
The effects of several substrates on the developed tension (DT) of isolated rat atria, made hypodynamic by the removal of glucose, were investigated. The addition of pyruvate, acetate, or butyrate at 5.5 mM, led to a partial recovery of the DT. Nevertheless, when they were incorporated in concentration of 11.0 mM, the recovery of DT was significantly smaller than that obtained with lower concentrations. The addition of 5.5 mM glucose restored the DT completely; whereas higher concentrations (11.0 mM) stimulated the DT above control levels, Mannose, at 5.5 mM, produced only a partial recovery of DT; whereas at a higher concentration (11.0 mM) it was also able to recover the DT completely. Although fructose at both concentrations did not produce a significant recovery of DT, it halted the depression caused by the absence of substrate. The atrial levels of ATP were decreased by the absence of glucose, and recovered by all the substrate studied, independently of their molarities and of the degree of contractile recovery attained. From the present results, it appears that glycolysis plays a fundamental role in the regulation of DT levels; and, furthermore, that the modification of ATP concentration is not the only mechanism by which different substrates can alter the DT of hypodynamic rat atria.
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