Induction of heat-shock proteins by glutamine. The 'feeding effect'

Subconfluent, log-phase Chinese hamster ovary cells induced the major heat-shock proteins (hsp) when cells were refed, 40 hours after seeding. This method of inducing heat-shock proteins was also obtained by refeeding with fresh serum-free media, but not with media with a long shelf life or with media prepared without glutamine. It was observed that addition of glutamine alone to cultures at 40 hours post-seeding induced heat-shock proteins. Addition of ammonium chloride, however, had no discernible effect on heat-shock protein synthesis. Northern blot analysis indicated that this phenomenon reflected an increase in the levels of message for the constitutive/inducible member of the hsp 70 family, but not the non-constitutive member. To determine the effect of this induction on heat sensitivity, unfed and 'heat-shock-induced' refed cultures were heated at 45 degrees C. No significant difference in cell survival was observed. Therefore glutamine is the necessary ingredient required for the induction of heat-shock proteins and this method of inducing heat-shock proteins does not alter heat sensitivity.