Intracellular responses of antibody-producing H69K-NGD transfectoma subjected to hyperosmotic pressure

Abstract

When subjected to hyperosmotic pressure by NaCl addition, H69K-NGD transfectoma, like KR12H-2 transfectoma, displayed decreased specific growth rate (p) and increased specific antibody productivity (q(Ab)): Elevation of medium osmolality from 280 mOsm/kg to 415 mOsm/kg decreased P by 79% in batch cultures of H69K-NGD transfectoma, while it increased q(Ab) 103%. However, unlike KR12H-2 tranfectoma, enhanced q(Ab) of H69K-NGD transfectoma at hyperosmolalities was not due to elevated levels of Ig mRNAs. In hyperosmotic cultures of H69K-NGD transfectoma, heavy-chain mRNA per cell was not enhanced with increasing osmolality. Hyperosmotic pressure was found to preferentially enhance immunoglobulin (Ig) translation rates of H69K-NGD transfectoma. However, under hyperosmotic pressure, the translation rate of Ig polypeptides was not enhanced as much as q(Ab). This result suggests that hyperosmotic pressure also influences the post-translational process. Taken together, the results obtained show that intracellular response of transfectomas to hyperosmotic pressure, in regard to the main intracellular steps of the antibody secretory pathway, is cell-fine dependent.