Uptake of bovine serum albumin by rainbow trout from hypersmotic solutions: a model for vaccinating fish.

Immersion of juvenile rainbow trout (Salmo gairdneri) in a solution containing either urea or sodium chloride at 1650 milliosmoles and 2 percent of bovine serum albumin (BSA) resulted in an uptake of BSA into the blood of the fish after a 3-minute exposure. Similar blood levels of BSA were also obtained by placing the fish in 1650 millosmoles of sodium chloride for about 2 minutes, and then immersing them in 2 percent BSA solution for 3 minutes. Uptake of BSA into the fish appeared to be primarily through the lateral line system and secondarily through the gills.