SEQUENCE AND EXPRESSION OF CDNA FOR PITUITARY ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE (PACAP) AND GROWTH HORMONE-RELEASING HORMONE (GHRH)-LIKE PEPTIDE IN CATFISH

Growth hormone-releasing hormone (GHRH) and pituitary adenylate cyclas e activating polypeptide (PACAP) are two neuropeptides that are associ ated with the release of pituitary growth hormone. Here a cDNA of 2501 base pairs encoding both a PACAP and a GHRH-like peptide was isolated from a brain cDNA library made from Thai catfish (Clarias macrocephal us). The organization is unlike that of the mammalian gene where PACAP and PACAP-related peptide (PRP) are encoded in one gene, and the GHRH peptide is on a separate gene. Northern analysis of catfish brain mRN A indicated that PACAP/GHRH-like mRNA has three sizes; bands of 6000, 2500, and 1000 bases suggest alternative splicing of the gene. Reverse transcriptase/PCR assay detected PACAP/GHRH-like mRNA in tissues from the brain, testis, ovary, and stomach, but not from the pancreas, pit uitary, muscle, and liver. Our hypothesis that the two mammalian genes encoding GHRH or PACAP originated from a gene duplication between fis h and tetrapods is supported by the present findings of similar mRNA o rganization and pattern of expression for the one fish gene and two ma mmalian genes.