Utilization of free fatty acids by diaphragm in vitro

Human and rat diaphragm and rat gastrocnemius muscle oxidize and esterify palmitate-1-C14. Incorporation of C14 was found to be in proportion to the palmitate present in the medium over a range of concentrations from 0.8 to 2.9 µEq/ml. Fasting increased C14O2 production but had no effect on esterification. Iodoacetate or an atmosphere of nitrogen inhibited esterification of palmitate but increased the amount of free fatty acid in the tissue. Insulin increased esterification, and this was enhanced by the addition of glucose. Glucose and insulin exerted a sparing action on the oxidation of glycerides by a tissue previously charged with palmitate-1-C14. Growth hormone administered in vivo over a period of 1 week or in vitro during incubation had no effect on esterification or metabolism of palmitate-1-C14.