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When subjected to hyperosmotic pressure by NaCl addition, H69K-NGD transfectoma, like KR12H-2 transfectoma, displayed decreased specific growth rate (μ) and increased specific antibody productivity (qAb): Elevation of medium osmolality from 280 mOsm/kg to 415 mOsm/kg decreased μ by 79% in batch cultures of H69K-NGD transfectoma, while it increased qAb by 103%. However, unlike KR12H-2 tranfectoma, enhanced qAb 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 qAb. This result suggests that hyperosmotic pressure also influences the posttranslational 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-line dependent.
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