The aim of this study was to re-assess whether alpha 2-adrenergic receptors were present in rat adipocytes, by using UK 14304, a new and very selective alpha 2-agonist. The following observations demonstrate the presence of functional alpha 2-adrenoceptors in rat adipocytes. (1) Adipocyte lipolysis was dose-dependently inhibited by UK 14304 (maximal effect 80% at 1 microM-UK 14304, 45% at 10 microM-UK 14304, under basal or theophylline-stimulated conditions respectively). (2) UK 14304 bound specifically to purified plasma membranes, with Bmax. = 744 fmol/mg of protein and KD = 9 nM. (3) The effect of UK 14304 was suppressed by alpha 2-antagonists. (4) Adrenaline inhibited lipolysis upon beta-adrenergic blockade (propranolol). (5) The anti-lipolytic effect of UK 14304 was modulated by the age of the rats.

No abstract

No abstract

No abstract

Under in vitro experimental conditions in which insulin increases adipose tissue lipoprotein lipase, cyclic GMP or dibutyryl cyclic GMP has no effect on this enzyme in rat adipose tissue fragments, or on either the intra- or extracellular forms of this enzyme in isolated fat cells. These results do not support the involvement of cyclic GMP in the insulin-stimulation of lipoprotein lipase in adipose tissue.