Localization of somatostatin mRNAs in the brain and pancreas of rainbow trout (Oncorhynchus mykiss)

Rainbow trout possess three distinct mRNAs, each encoding a separate precur sor: PPSS I, which contains a 14-amino acid sequence at its C-terminus (som atostatin-lit) that is highly conserved among vertebrates, as well as two o thers, PPSS II ' and PPSS II ", both containing [Tyr(7), Gly (10)]-somatost atin-14 at their C-terminus. In this study, we used RNA template-specific P CR and in situ hybridization to determine the distribution and cellular loc alization of PPSS mRNAs in the brain and Brockmann body of rainbow trout. P PSS I, PPSS II ' and PPSS II " were expressed in the Brockmann body and pit uitary; the expression of PPSS mRNAs in the brain was region specific. PPSS I mRNA was expressed in the Brockmann body predominantly by cells other th an those that expressed PPSS IIs; however, there were several instances whe re PPSS I and PPSS IIs were co-expressed within the same cell. Of the PPSS II-expressing cells, many were observed to express both PPSS II ' and PPSS II " mRNA; however, some cells expressed only PPSS II ' mRNA, while other c ells expressed only PPSS II " mRNA. In the brain, PPSS I mRNA was expressed in the optic tectum (OT) and in many hypothalamic nuclei, including the nu cleus rotundus (NR), nucleus anterioris hypothalami (NAH), nucleus anterior tuberis (NAT), nucleus lateral tuberis (NLT), as well as in the pituitary (adenohypophysis). PPSS II " mRNA was present in the same regions as PPSS I mRNA; however, PPSS II ' mRNA was present primarily in OT, NAT, NLT and ad enohypohysis. These results indicate that PPSS mRNAs are expressed differen tly by different cells, suggesting that cell-specific mechanisms are involv ed with the control of PPSS expression and that particular biological respo nses may be associated with a specific SS isoform. (C) 2001 Elsevier Scienc e Inc. All rights reserved.