Hyperosmotic Infiltration: Factors Influencing Uptake of Bovine Serum Albumin by Rainbow Trout (Salmo gairdneri)

Infiltration of bovine serum albumin (BSA) into the blood of rainbow trout (Salmo gairdneri) by hyperosmotic infiltration (HI) was studied by varying the osmotic pressure, immersion time, pH, temperature, stress, vacuum, and fish size. Compared with uptake of BSA from water solutions, about 1400 mosM (4.51%) NaCl was required to increase the plasma level of BSA during a 3-min immersion. Higher osmotic pressures resulted in higher plasma-BSA levels, but the uptake of BSA was limited by the length of time that fish could tolerate the high NaCl concentration. Comparison of immersion time in the solutions of the two-step HI method showed that maximum infiltration occurred after a 2–3-min bath in the 5.32% NaCl solution and only 30 s in the 2% BSA solution. Alkaline solution (pH 9) enhanced BSA uptake in the one-step method, but the two-step method was most effective if the NaCl solution was pH 9 and the BSA solution pH 5. BSA uptake was directly proportional to water temperature from 4 to 20 °C. Preimmersion stress, and injection of 10 μg epinephrine, reduced BSA uptake; vacuum and fish weight (2–8 g) had no effect on uptake of BSA. Hyperosmotic infiltration may be useful for mass delivery of vaccines, pharmaceuticals, and other materials. Key words: hyperosmotic infiltration, bovine serum albumin, osmotic pressure, vaccines, immersion, rocket immunoelectrophoresis