TY - JOUR T1 - Effect of K<sup>+</sup>, Valinomycin, Tetraphenylborate and Ouabain on Lipolysis by White Fat Cells JF - Molecular Pharmacology JO - Mol Pharmacol SP - 349 LP - 357 VL - 4 IS - 4 AU - JOHN N. FAIN Y1 - 1968/07/01 UR - http://molpharm.aspetjournals.org/content/4/4/349.abstract N2 - The omission of K+ from the phosphate buffer used for isolation and incubation of white fat cells potentiated the lipolytic action of theophylline but inhibited that of catecholamines. Omission of K+ reduced the lipolytic action of growth hormone and glucocorticoid in the absence of glucose from the medium. Valinomycin, a macrocyclic antibiotic which increases the K+ permeability of natural and artificial lipid membranes, inhibited the lipolytic action of theophylline if K+ was present in the medium. In the absence of K+ valinomycin had the opposite effect. Valinomycin did not mimic the stimulatory effect of insulin on glucose metabolism in buffer plus K+ where it acted as an antilipolytic agent. Ouabain stimulated glucose metabolism and inhibited the lipolytic action of norepinephrine only if K+ was present in the buffer. However, ouabain potentiated the lipolytic action of theophylline. These results indicate that the activation of lipolysis in fat cells does not have an absolute dependency upon K+ but can be indirectly influenced by alterations in medium K+ or by drugs which influence K+ influx and efflux across cell membranes. ER -