The effect of prostaglandins on ox pituitary content of adenosine 3′:5′-cyclic monophosphate and the release of growth hormone

摘要

p1. An assay, based on competition between adenosine 3′:5′-cyclic monophosphate (cyclic AMP) and cyclic [sup3/supH]AMP for binding to a rabbit skeletal muscle protein, has been used to measure tissue contents of cyclic AMP. The assay has a sensitivity of 0.05pmol of cyclic AMP. Cyclic GMP and cyclic CMP have 0.5%, and cyclic IMP 6.5%, of the ability of cyclic AMP to displace cyclic [sup3/supH]AMP from binding protein; AMP, ADP and ATP have no effect. 2. By using this method, the cyclic AMP content of ox pituitary slices exposed to prostaglandin was determined; release of growth hormone was measured by radioimmunoassay. 3. Release of growth hormone was increased by 45min incubation in 1μm-prostaglandin Esub2/sub in the absence of theophylline, or in 10nm-prostaglandin Esub2/sub, 0.1μm-prostaglandin Asub1/sub or 1μm-prostaglandin Bsub1/sub in the presence of 0.5mm-theophylline. 4. Pituitary cyclic AMP content was increased by 10min incubation in 1μm-prostaglandin Esub2/sub in the absence of theophylline, or in 0.1μm-prostaglandin Esub2/sub in the presence of 0.5mm-theophylline. 5. The maximum increase in cyclic AMP content was observed 10min, and significant changes in growth hormone release 30min, after introduction of prostaglandin Esub2/sub. 6. The increase in pituitary cyclic AMP content, but not in the rate of release of growth hormone, was observed in the absence of external Casup2+/sup. 7. The stimulation of release of growth hormone by prostaglandin was decreased by preincubation of tissue for 2h in colchicine (100μm) or cytochalasin B (10μg/ml). 8. These results support the suggestion that increased release of growth hormone after treatment with prostaglandin is the result of increased tissue cyclic AMP content, and possibly involves a microfilamentous or microtubular protein./p