Ouabain and digitoxin as modulators of chick embryo cardiomyocyte energy metabolism

The effects of 0.1 nmol/l ouabain (CAS 630-60-4) and digitoxin (CAS 71-63-6) on oxygen consumption rate (OCR) and the contractility of cultured chick embryo cardiomyocytes were investigated using a perfusion system which allowed microscopic observation during the experiment. contractility was assessed by a novel image analysis procedure. During substrate free perfusion the OCR was increased on application of 0.1 nmol/l ouabain or digitoxin for 60 min, whilst contractility was not affected. Digitoxin (0.1 nmol/l) elicited no change in the OCR in the presence of glucose, pyruvic acid, lactic acid and caprylic acid. Ouabain (0.1 nmol/l) did not affect the OCR or contractility in the presence of glucose, pyruvic acid and lactic acid, however together with caprylic acid the OCR was increased significantly. These results demonstrate a hitherto unknown stimulation of fatty acid utilization by low concentrations of ouabain.