E. Gordon Grau


Environmental Physiology and Comparative Endocrinology of Estuarine Fish



HIG 238


(808) 956-7031


(808) 956-3014

Research Interests

The neuroendocrine system regulates development and physiology in fish and coordinates their interactions with their environment. Our studies are based on the idea that reproduction, development, immune function and environmental adaptation are regulated through the orderly release of hormones by the neuroendocrine system, which integrates information from genes and the environment. Such studies can improve the way we utilize and protect the marine organisms, the renewable resources of marine environments. Studies in developmental endocrinology can be used to increase the food supply through aquaculture without compromising environmental health. These studies can also provide new avenues for restoring populations of endangered species, for limiting noxious organisms and for clarifying the effects of endocrine-disrupting chemicals. These chemicals enter the environment through human activity. Their negative impact on marine animals, including fish, can be profound because hormones play a crucial role in controlling development.

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.

Selected Publications

Seale, A. P., Riley, L. G., Leedom, T. A., Kajimura, S., Dores, R. M., Hirano, T., and Grau, E. G. 2001. Effects of environmental osmolality on release of prolactin, growth hormone and ACTH from the tilapia pituitary. Gen. Comp. Endocrinol. in press.

Seale, A. P., Itoh, T., Moriyama, S., Takahashi, A., Kawauchi, H., Sakamoto, T., Fujimoto, M., Riley, L. G., Hirano, T., and Grau, E. G. 2001. Isolation and Characterization of a Homologue of Mammalian Prolactin-Releasing Peptide from the Tilapia Brain and Its Effect on Prolactin Release from the Tilapia Pituitary. Gen. Comp. Endocrinol. Accepted for publication.

Basu, N., Nakano, T., Grau, E. G. and Iwama, G. K. 2001. The effects of cortisol on heat shock protein 70 levels in two fish species. General and Comparative Endocrinology, in press.