EFFECTS OF OUABAIN AND K⁺ -FREE MEDIUM ON ACTIVATED LIPOLYSIS AND EPINEPHRINE-STIMULATED GLYCOGENOLYSIS

¹ Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, New York

In a first series of experiments, epididymal fat pads of rats were incubated for 2 hr in Krebs-Ringer phosphate adjusted to pH 7.4. Ouabain (10^-4 M) inhibited significantly (by 40%) glycerol release due to epinephrine (10^-5 M), but not glycerol release due to norepinephrine (10^-5 M). Similar inhibition of epinephrine-induced lipolysis was observed when the fat pad was incubated in K⁺-free medium. Release of glycerol induced by theophylline (10^-3 M) was not altered by ouabain or by K⁺-free medium, whereas the lipolytic activity of a derivative of cyclic 3', 5'-AMP (adenosine 3', 5'-phosphate) (10^-3 M) was significantly increased in the presence of ouabain or in K⁺-free medium. In a second series of experiments, measurements of glycogen concentration and specific activity in diaphragm muscle indicated that epinephrine-induced glycogenolysis was significantly inhibited by ouabain or K⁺-free medium. These results could be interpreted as indicating that ouabain and K⁺-free medium might exert their inhibiting effects in glycogenolysis and lipolysis through decreased hydrolysis of adenosine triphosphate and decreased formation of cyclic 3,5 AMP.