Growth hormone and prolactin expression during environmental adaptation of gobies

Growth hormone and prolactin belong to a family of hormones that share functional similarities including roles in environmental adaptation. Gobiidae are widely distributed ecologically and have developed diverse functions to adapt to the various environments, which provide unique models for studies on the environmental adaptations. In Mugilogobius abei, for example, growth hormone may enhance nitrogen metabolism including glutamine/urea synthesis for ammonia tolerance, and consequently promote growth in polluted environments. In amphibious euryhaline mudskipper, pituitary prolactin seems to be involved in freshwater and terrestrial adaptation, whereas growth hormone in seawater adaptation. During terrestrial adaptation, pituitary prolactin was induced, possibly by brain prolactin-releasing peptide. Prolactin-releasing peptide - prolactin axis in the intestine operated during freshwater adaptation. Intestinal prolactin seems to be expressed in the epithelia, especially in the mucous cells. Thus, the prolactin-releasing peptide - prolactin axes in various organs may play an organ-specific role.