Regulation of porcine adipose tissue lipolytic activity by adrenergic agonists and antagonists

1. Several beta-adrenergic agonists yielded quantitatively and qualitatively different lipolytic potencies and efficacies when incubated with porcine adipose tissue slices in the presence and absence of theophylline in vitro. Some agonists were inactive without theophylline but were active with theophylline. 2. However, activity in vitro measured with theophylline was no more closely related to acute observations in vivo than activity measured in vitro without theophylline. 3. Classification of receptor subtypes or agonists and antagonists as specific for receptor subtypes could be totally different in the presence and absence of theophylline, depending on the specific agonists or antagonists selected for such studies in vitro.