Evidence of a reproduction-related function for pituitary adenylate cyclase-activating polypeptide-related peptide in...

Pituitary adenylate cyclase-activating polypeptide (PACAP) is synthesized from a precursor, which includes the PACAP-related peptide (PRP; formerly known as GHRH-like peptide). PRP can act as a hypophysiotropic factor in teleosts by stimulating GH secretion. However, no information points to this peptide as a regulator of reproduction. Recently, the blue gourami PRP-PACAP cDNA was cloned and found to be expressed in the brain. Thus, the aims of the present study were to investigate the PRP-PACAP gene expression pattern during sexual behavior and oogenesis, and to learn its effect on pituitary hormonal transcription in pituitary cells. Examination of the PRP-PACAP expression profile during sexual behavior and oogenesis revealed that PRP-PACAP mRNA levels were higher in mature non-reproductively active males than in nest builders and juveniles; and higher in females with oocytes in the final maturation stage than in vitellogenic individuals. Stimulation of pituitary cells with blue gourami PRP (bgPRP) caused an increase in βLH subunit transcription levels only in females, whereas in males, it only brought about a rise in GH mRNA levels. These data were further supported by the presence of PRP receptor in the pituitary cells. Therefore, we propose that as a hypophysiotropic factor in the blue gourami, bgPRP may act differently on the gonadotropic axes in females and males, up-regulating gonadotropin mRNA in females and GH mRNA in males. This research provides a basis for the further understanding of the integrative network that regulates growth and reproduction, which may contribute to hormonal treatments and manipulations in aquaculture.