The Effect of Hormones on the Osmoregulatory Properties of the Intestine of the Euryhaline European Eel, Anguilla anguilla

The gastrointestinal tract is a key organ involved in maintaining salt and water balance in the euryhaline eel as it migrates between fresh and seawater. In the freshwater environment there is an osmotic gain of water over semi-permeable membranes. However teleost fish maintain osmotic balance by drinking the environmental medium, sodium chloride and other ions are actively absorbed in the intestine and water follows. This is controlled by a number of hormones, including cortisol and angiotensin II, which enhance the ability of fish to survive in these environmental extremes. Hormones such as cortisol and angiotensin II may affect intestinal sodium and water transport and therefore could be essential in the osmoregulatory plasticity of the animal during migration. Using intra-peritoneal implanted mini-osmotic pumps was the effects of singly infused cortisol and angiotensin II was investigated on excised stripped and everted intestines. Investigation of sodium and water uptake was investigated in specific regions previously identified as having high transport capacity, inhibitable by drug application, and compared between groups of control, and hormonally infused animals.