Lipolytic activity of porcine adipose tissue after preincubation

1. The stimulated lipolytic rate in porcine adipose tissue slices was markedly increased after preincubation with or without isoproterenol. 2. Preincubation with and without insulin, dibutyryl-cAMP or theophylline suggested that the activation of the stimulated rate resulted from inhibition or inactivation of cAMP-phosphodiesterase activity during preincubation. 3. Preincubation with isoproterenol also caused activation of the basal (no exogenous hormone) lipolytic activity. 4. However, much of this activation appeared to result from carry-over of isoproterenol into the incubation medium because it could be lowered by additional washing of the tissue, by lower isoproterenol concentration or by propranolol.