ADRENERGIC-LIPOLYSIS IN GUINEA-PIG IS NOT A BETA(3)-ADRENERGIC RESPONSE - COMPARISON WITH HUMAN ADIPOCYTES

beta(3)-Adrenoceptor agonists are potent lipolytic activators in rats, but they are only weak stimulators in human adipocytes, indicating in terspecies differences in the adrenergic regulation of lipid mobilizat ion. Like human but not rat adipocytes, guinea pig fat cells were poor ly responsive to the beta(3)-agonists BRL-37344, CGP-12177, SR-58611, and ICI-215001, acid metabolite of ICI-D7114. In guinea pigs, the beta (1)-agonist dobutamine was more lipolytic than the beta(2)-agonist pro caterol. Anatomic location of fat deposits was without major influence on the beta-adrenergic responsiveness. Weak responses to beta(3)-agon ists were found whatever the sex or the age (from 2 days to 16 mo) of the animals. Even in the interscapular brown adipose tissue, which is well known in rats for its beta(3)-adrenergic responsiveness, a blunte d response to BRL-37344 was observed. The alpha(2)-adrenergic antilipo lytic effect and receptor number were smaller in guinea pig than in hu man adipocytes, but the beta-adrenergic receptor number was similar in the two species. Thus guinea pig adipocytes resemble human fat cells when their weak beta(3)-adrenergic responsiveness is considered.