Functional and Metabolic Consequences of Vitamin B-6 Deficiency in the Rat Heart

The cardiac functional and metabolic consequences of pyridoxine deficiency were studied in rats maintained on a pyridoxine-deficient diet for 10 weeks. Because food intake was diminished in the pyridoxine-deficient rats, a second group of animals was fed a diet restricted to the intake of the pyridoxine-deficient animals. The inotropic response (developed pressure) to an isoproterenol or Ca²⁺ concentration response curve was measured simultaneously with high energy phosphate levels using a modified Langendorf apparatus and ³¹P nuclear magnetic resonance spectroscopy. The inotropic response to Ca²⁺ and isoproterenol was significantly decreased relative to controls in both the food-deprived and the pyridoxine-deficient groups. Developed pressure after adrenergic stimulation was significantly less in the pyridoxine-deficient than in the food-deprived animals. Phosphocreatine and ATP levels were maintained and did not differ among the control, pyridoxine-deficient, and food-deprived groups during isoproterenol and Ca²⁺ stress, implying that the diminished inotropy was not due to an abnormality in generation of high energy phosphate levels.