Effects of somatostatin and urotensin II on tilapia pituitary prolactin release and interactions between somatostatin, osmotic pressure Ca++, and adenosine 3',5'-monophosphate in prolactin release in vitro.
Both somatostatin (SRIF) and urotensin II, a dodecapeptide from the teleost caudal neurosecretory system, inhibit PRL release from the organ-cultured rostral pars distalis of the tilapia, Sarotherodon mossambicus, in a dose-related manner. The inhibitory action of SRIF on PRL release was completely prevented by the presence of the calcium ionophore A23187. PRL release was also blocked when Ca++ was excluded from the incubation medium, even in the presence of the ionophore. Both dibutyryl cAMP (dbcAMP) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, alone or in combination, stimulated PRL release during incubation in high osmotic pressure medium. The effect of dbcAMP appeared to be dose related. Together, dbcAMP and 3-isobutyl-1-methylxanthine were also effective in preventing the inhibition of PRL release by SRIF. These results are consistent with the notion that Ca++, and possibly cAMP, may be important mediators of PRL secretion, and it is likely that SRIF may inhibit PRL release by blocking a Ca++- or cAMP-mediated mechanism.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D005399:Fishes; D009997:Osmotic Pressure; D010455:Peptides / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D013004:Somatostatin / Q000494:pharmacology*; D014579:Urotensins / Q000494:pharmacology*
D010455:Peptides; D014579:Urotensins; D000001:Calcimycin; D013004:Somatostatin; D003994:Bucladesine; D011388:Prolactin; C029677:urotensin II; D000242:Cyclic AMP; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine