Decrease of prostaglandin E2 receptor binding is accompanied by reduced antilipolytic effects of prostaglandin E2 in isolated rat adipocytes.

Abstract

The effect of treatment of isolated rat adipocytes with prostaglandin E2 (PGE2) on subsequent [3H]PGE2 binding was studied. In addition, the antilipolytic effects of was studied. In addition, the antilipolytic effects of PGE2, adenosine, and insulin were studied in control and PGE2-treated adipocytes. Treatment of adipocytes with PGE2 (1 microM) decreased the binding of [3H]PGE2 by 61% (from 11.0 to 4.6 fmol/10(6) cells, P less than 0.005). Scatchard analysis of the binding data demonstrated that the decrease of PGE2 receptor binding was due to a decrease in the apparent number of PGE2 receptors while the apparent receptor affinity was unaltered. Reduction of the PGE2 receptor binding was specifically regulated inasmuch as structurally related compounds such as PGF2 alpha and arachidonic acid had only minor effects on subsequent [3H]PGE2 receptor binding. Reduction of the available receptor number was associated with a significant decrease in the antilipolytic effect of PGE2 on the isoproterenol-stimulated lipolysis (P less than 0.05). The maximal antilipolytic effect of PGE2 was decreased by 45%. Desensitization of the biological effect of PGE2 (antilipolysis) was only partially specifically regulated inasmuch as the antilipolytic compound phenylisopropyladenosine also had reduced antilipolytic effect in PGE2-treated cells. However, the antilipolytic effect of insulin was similar in control and PGE2-treated cells. It was found that the PGE2-induced decrease of [3H]PGE2 receptor binding may be due to a very tight coupling between the PGE2 molecule and its specific receptor. This tight coupling may then represent an occupancy of the receptor rather than a true loss of receptors.(ABSTRACT TRUNCATED AT 250 WORDS)