Hawai'i Institute of Marine Biology P.O. Box 1346 Kane'ohe, Hawai'i 96744 phone: (808) 236-7406 FAX: (808) 236-7443
The regulation of salt and water balance is a fundamental requirement of life. The structure and function of macromolecules depend closely on their interactions with water and its solutes. Few factors affect the distribution and evolution of an organism as extensively as osmoregulation. Thus, organisms invest considerable energy in controlling precisely the composition of both intracellular and extracellular fluids. In fish, osmoregulation typically consumes 25-50% of the total metabolic output, possibly the largest single component. Osmotic equilibrium is maintained only through the precise interplay of a major portion of the neuroendocrine array. Indeed, the maintenance of osmotic balance in seriously ill patients is among the most difficult challenges in medicine. In view of the cost and importance of osmoregulation, it may seem ironic that the mechanisms that monitor and regulate osmotic balance are so poorly understood. Closer attention reveals the impediment, the typically complex structure and arrangement of osmoreceptive cells and tissues. These problems are obviated by the use of the osmosensitive prolactin cell of a fish pituitary. Prolactin plays a fundamental role in freshwater osmoregulation, and prolactin cells are directly sensitive to extracellular osmolality. Our studies are aimed at elaborating the cellular mechanisms that mediate this osmoreceptive response. The information these studies provide has found useful application in such diverse areas as biotechnology, medicine and aquaculture.
Morrey C, Nakamura M, Kobayashi T, Grau EG, Nagahama Y. 1998. P450scc-like immunoreactivity throughout gonadal restructuring in the protogynous hermaphrodite, Thalassoma duperrey. Int J Devel Biol 42:811-816.
Shepherd BS, Sakamoto T, Mori I, Nishioka RS, Richman NH III, Madsen S, Hirano T, Bern HA, Grau EG. 1997. Somatotropic actions of the homologous growth hormone (tGH) and prolactins in the euryhaline tilapia, Oreochromismossambicus. PNAS 94:2068-2072.
Weber GM, Powell JFF, Park M, Fisher WH, Rivier JE, Nanakorn U, Parhar IS, Grau EG, Sherwood NM. 1997. Primary structures for three gonadotropin-releasing hormone (GnRH) molecules and evidence that GnRH functions as a prolactin-releasing factor in tilapia. J Endocrinol 155:121-132.