Rainbow trout (Oncorhynchus mykiss) possess two somatostatin mRNAs that are differentially expressed.

Previously, we isolated a 624-bp cDNA encoding for a 115-amino acid preprosomatostatin containing [Tyr7,Gly10]-somatostatin (SS)-14 (now designated PPSS-II') obtained from the endocrine pancreas (Brockmann bodies) of rainbow trout. In this study we have characterized a second cDNA obtained from trout pancreas that is 600-bp in length and encodes for a 111-amino acid precursor containing [Tyr7,Gly10]-SS-14 (PPSS-II''). The nucleotide and amino acid identity between the two cDNAs is 82.3 and 80.5%, respectively. Both PPSS-II' and PPSS-II'' mRNA were present in esophagus, pyloric ceca, stomach, upper and lower intestine, and pancreas, whereas only SS-II" mRNA was present in brain. PPSS-II'' mRNA was more abundant than PPSS-II' mRNA in pancreas, whereas PPSS-II' mRNA was more abundant than PPSS-II" mRNA in stomach. Fasting increased pancreatic PPSS-II'' mRNA levels but had no effect on the levels of PPSS-II' mRNA. These results indicate the existence of two nonallelic pancreatic SS-II genes that are differentially expressed, both in terms of distribution among tissues and in terms of relative abundance within the tissues.