ABSTRACT
A-549 cells of human lung adenocarcinoma were subjected to heat shock (30 min, 44 degrees C) which caused substantial decreases in the rates of biosynthesis of the great bulk of cellular proteins with simultaneous increases in the synthesis rates of the 70 kDa protein predominantly localized in cell cytosol. By the 6th hour after the heat shock cessation this protein synthesis reached its maximum; by the 18th hour it was no longer detectable, while the protein itself was not denatured. During the recovery after the heat shock the ability of the serum-free culture medium conditioned by A-549 cells in autocrine regulation of [3H]thymidine incorporation into DNA and [3H]leucine incorporation into proteins changed also. The conditioned medium obtained within 1-3 hours after the heat shock did not influence the intensity of DNA synthesis, while the medium obtained 4-48 hours after the heat shock stimulated this process, the maximal effect (3.3-fold stimulation) being observed in the case of the 48-hour conditioned medium. Temporary (1 hour) acidification of the conditioned media down to pH 2.0 resulted in complete inhibition of the stimulating activity. Besides, these media acquired an ability to inhibit [3H]thymidine incorporation into the DNA of tracer cells. Study of effects of conditioned media on the rate of [3H]leucine incorporation into A-549 cell proteins revealed that the media obtained 1-4 hours after the heat shock inhibited this process, while the media obtained 6-18 hours thereafter stimulated it 1.2-2.1-fold. In the test systems under study temporary acidification of the media increased their stimulating influence on [3H]leucine incorporation into cellular proteins.
