PULSATILE GROWTH-HORMONE SECRETION IS MARKEDLY ATTENUATED AFTER ADRENALECTOMY AND CAN BE RESTORED WITH DEXAMETHASONE

Literary data indicate that glucocorticoids enhance pituitary growth h ormone (GH) response to growth hormone releasing factor (GRF). In the present studies we have investigated the effect of adrenalectomy and d examethasone (DEX) supplementary treatment on the episodic secretion o f GH. Further we studied, by means of reverse hemolytic plaque assay ( RHPA), the effect of in vitro DEX treatment on basal and GRF-induced s ecretion of somatotropes obtained from both intact and adrenalectemize d (ADX) male rats. The episodic pattern of CH release was evident in A DX animals, however the mean and the peak levels were significantly lo wer than in controls. Daily treatment of ADX rats with DEX (0.25 mg/kg b.w.) almost completely restored maximum as well as mean CH levels, A drenalectomy significantly decreased the secretory activity and CRF re sponsiveness of somatotropes in vitro. DEX added to the culture comple tely reversed the adrenalectomy-induced decline in GH secretion, The o bservations suggest that (i) episodic GH secretion is influenced by gl ucocorticoids; (ii) a normal amount of CH secreted by somatotropes and a normal responsiveness of GH cells to CRF requires a certain level o f glucocorticoids; (iii) cellular heterogenity of somatotropes may pro vide the basis for episodic release of GH.