Improved bioavailability of orally delivered peptides and polypeptides in teleost fish

A gonadoliberin analogue (GnRHa) whose biological role is the stimulation o f gonadotropin (GTH II) secretion, has been encapsulated together with inte stinal absorption enhancers and proteolytic enzyme inhibitors. The capsules have been coated to prevent their solubilization at acid pH in the stomach . After oral delivery of the capsules by forced-feeding, high GnRHa intesti nal absorption and high bioavailability in the blood results. GTH II secret ion was stimulated in a dose-dependent manner by the orally delivered GnRHa in three species having different digestive tract structures and different feeding habits: the rainbow trout, the common carp and the African catfish . In addition, the oral delivery of GnRHa also results in the induction of ovulation in all three species at doses similar to those usually used to in duce spawning in these species. There was no competition of nutrient given together with the microcapsules on GnRHa absorption. From these results, it becomes possible to develop special diets containing microencapsulated bio active peptides for use in therapy or to modify nonvital functions in fish. In the present case, an orally-induced ovulation treatment will be develop ed.