Abstract
Abstract The effect of dibutyryl cyclic AMP (N6, O2'-dibutyryl cyclic adenosine 3', 5'-monophosphate) on protein synthesis and release has been studied in rat anterior pituitary gland. In unstimulated pituitary halves, incorporation of radioactive amino acids is maintained at a constant level for at least 5 hours. In response to dibutyryl cyclic AMP (5 mm), there is a 50 to 80% increase in the rate of incorporation into trichloracetic acid-insoluble proteins after 2 to 3 hours of incubation of male adenohypophyseal tissue. Concurrently, up to 30 min after addition of the cyclic nucleotide, there is a 275% stimulation of newly synthesized protein released into the medium, the effect being already maximal at 4 min. Actinomycin D, at a dose which inhibits RNA synthesis to less than 10% of the control rate, is without effect on the stimulatory action of dibutyryl cyclic AMP on either total protein synthesis or release. It is concluded that dibutyryl cyclic AMP stimulates both protein synthesis and release in the anterior pituitary gland, the effect on protein synthesis being probably exerted at the level of translation.
Highlights
In unstimulated pituitary halves, incorporation of radioactive ammo acids is maintained at a constant level for at least 5 hours
Incorporation of r4C-amino acids into the protein fraction released into the incubation medium was increased by 71 to 129% with dibutyryl cyclic AMP
The over-all stimulation of protein synthesis obtained by the summation of the released and of the remaining intracellular radioactive protein varied between 26 and 39%
Summary
The effect of dibutyryl cyclic AMP (N6,02’-dibutyryl cyclic adenosine 3’,5’-monophosphate) on protein synthesis and release has been studied in rat anterior pituitary gland. Synthetic thyrotropin-releasing factor increased adenyl cyclase activity in rat anterior pituitary tissue in vitro.a. As mediator of the action of the adenohypophysiotropic hormones of the hypothalamus, cyclic AMP could control the synthesis or the release of pituitary hormones or both mechanisms. The present studies were aimed at investigating the effect of cyclic AMP on protein synthesis and release in the rat anterior pituitary gland and at obtaining information about the site of action of cyclic AMP in this tissue. AMP stimulates both protein synthesis and release in anterior pituitary tissue in vitro This stimulatory effect is not blocked by concentrations of Actinomycin D that almost completely inhibit RN-4 synthesis, suggesting an effect at the translational level
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