Prostaglandin E2 increases adenosine 3',5'-monophosphate concentration and binding-site occupancy, and stimulates serotonin-N-acetyltransferase activity in rat pineal glands in vitro.
The effects of prostaglandins (PGs) on rat pineal metabolism were examined in vitro. PGE2 (0.01-1 microM) increased the activity of serotonin-N-acetyltransferase (SNAT), the stimulation curve exhibiting a maximum at 0.1 microM. PGE1 increased SNAT activity only at the highest dose (1 microM) whereas PGF2 alpha, 15-keto-PGF2 alpha or PGI2 did not affect the enzymic activity. The stimulation of SNAT activity brought about by PGE2 in pineals from ganglionectomized rats was greater than in sham-operated controls at all the doses studied, suggesting that the observed effect is predominantly post-synaptic. Only PGE2 significantly increased pineal cAMP accumulation in vitro at doses between 0.01 and 1 microM, and depressed the unoccupied cAMP-binding sites in pineal 900 g supernatants. The total number of cAMP-binding sites remained unaltered after incubation of PGE2. The present observations together with the previously reported NE-induced release of PGs in incubated pineal glands, the occurrence of pineal PG-binding sites and the indomethacin blockade of the nocturnal rise of pineal SNAT and melatonin content, support a role for PGs in the control of melatonin synthesis.
D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D001665:Binding Sites; D000242:Cyclic AMP / Q000378:metabolism*; D015232:Dinoprostone; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D010870:Pineal Gland / Q000187:drug effects* / Q000378:metabolism; D011458:Prostaglandins E / Q000494:pharmacology*; D011465:Prostaglandins, Synthetic / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D011458:Prostaglandins E; D011465:Prostaglandins, Synthetic; D000242:Cyclic AMP; D000123:Acetyltransferases; D001191:Arylamine N-Acetyltransferase; D015232:Dinoprostone