| Abstract: | Effects of exogenous prostaglandin E2 (PGE2) on rates of lipolysis in sections of subcutaneous adipose tissue biopsied from fed and fasted Holstein steers were determined. The interaction of PGE2 with several exogenous effectors of lipolysis and of the adenylate cyclase-cAMP system also was measured. Epinephrine increased basal (nonstimulated) lipolysis approximately one-fold. Prostaglandin E2 had no effect on either basal or epinephrine-stimulated lipolysis. Dibutyryl cAMP increased rate of lipolysis .4-fold, whereas theophylline increased lipolysis more than one-fold. Theophylline had an additive effect on epinephrine-stimulated lipolysis. Dibutyryl cAMP increased theophylline-stimulated lipolysis but not epinephrine-stimulated lipolysis. Prostaglandin E2 had no effect on epinephrine-, dibutyryl cAMP- or theophylline-stimulated lipolysis. Fasting decreased basal lipolysis by 40%. Furthermore, lipolysis in tissue incubated with PGE2, epinephrine or PGE2 plus epinephrine decreased from 30 to 50% upon fasting. As also shown with tissue from fed steers, PGE2 did not alter basal or epinephrine-stimulated lipolysis in tissue from fasted steers. Influences of exogenous effectors on lipolysis in adipose tissue from fed and fasted steers indicate that PGE2 does not control the adenylate cyclase-cAMP system that regulates lipolysis in bovine adipose tissue. |
