The study also sought to determine if sodium cyanide (NaCN) -- an inhibitor of oxidative metabolism V decreases activity of the glycolytic pathway and cardiac performance in both sexes, and if males possess a larger outermost (epicardial) layer of the ventricle vs. the inner endocardium layer. The trout heart is a composite organ and layer distinction is important because the epicardium, much like the human heart, receives oxygenated blood via the coronary circulation. Conversely, the endocardium is supplied by only deoxygenated blood returning from the rest of the body. Not surprisingly, the authors expect there to be corresponding layer differences in energy production and function.
Uniform ventricle strips or transverse rings were cut from 10-12 month old, hatchery raised, sexually-immature male and female rainbow trout. Each strip was prepared in one of two ways: (1) incubated without stimulation (i.e., ventricle strips were incubated in a respiration cell containing an oxygenated buffer solution with glucose as the energy substrate). Oxygen consumption was measured using a calibrated oxygen electrode and data acquisition system; or (2) electrically-paced (i.e., ventricle strips were electrically-stimulated at physiological rates and temperature in tissue baths containing buffer, with (a) glucose and (b) glucose + DCA (dichloroacetate, an activator of PDH and a therapeutic drug used to treat human heart disease and cancer), or (c) glucose + NaCN under oxygenated and hypoxic conditions.
The researchers measured several indices of contractile performance (resting tension, twitch force, post-rest potentiation and other variables. Frozen samples of ventricle tissue were homogenized and assayed for citrate concentration.
Contact: Donna Krupa
American Physiological Society