Structural and biochemical analyses of cardiac ventricular enlargement in cold-acclimated striped bass

and biochemical analyses of cardiac ventricular enlargement in cold-acclimated striped bass. Am. J. PhysioZ. 273 (Regula-tory Integrative Camp. Physiol. 42): R252-R258, 1997.-We examined effects of temperature acclimation on ultrastruc-tural characteristics of cardiac myocytes and maximal activi-ties of metabolic enzymes in cardiac tissue of striped bass (Morone saxatilis). Ventricular mass and ventricular mass divided by body weight were significantly increased (29 % and 40%, respectively) in animals acclimated to cold (5°C) vs. warm temperatures (25°C). Mean myocyte diameter was increased at cold temperature (3.47 t 0.14 vs. 2.98 _t 0.08 pm), which is sufficient to explain the increase in ventricular mass. Ventricular enlargement did not alter volume densities of mitochondria, myofibrils, protein concentration, or citrate synthase activity. Thus total volume of mitochondria an