THE TEMPORAL RELATIONSHIPS OF SYNTHESIS AND PHOSPHORYLATION IN STRESSPROTEINS 70 AND 90 IN AGED CALORIC RESTRICTED RATS EXPOSED TO BLEOMYCIN

A single intraperitoneal injection of the human therapeutic drug bleom ycin (BL) was administered to three groups of male Fischer 344 rats at time 0, and the incorporation of [S-35]methionine (''synthesis'') and phosphorylation patterns of stress proteins (sps/hsps) from bone marr ow cells were analyzed over time by two-dimensional electrophoresis an d fluorography. Two groups of rats, young ad libitum (Y/AL - 3 months) and old ad libitum (O/AL - 28 months), had free access to rat chow, a nd a third group of old rats (O/CR - 28 months) were maintained on a c aloric restricted intake (60% of the AL diet). The administration of B L in Y/AL, O/AL and O/CR animals activated the S-35-labeling of sp 90 which reached a peak at 4 hours. Labeling of sp 90 was significantly g reater in Y/AL compared to O/AL, and the incorporation pattern of O/CR was intermediate to Y/AL and O/AL animals. All labeling of sp 90 in e ach group had disappeared by 10 hours after BL administration. Stress protein 70x (inducible form) in these three animal groups displayed a similar pattern of S-35-incorporation, but the amount of labeling was less than that of sp 90. No labeling of sp 70x remained by 13 hours af ter BL administration. Phosphorylation ([P-32] phosphate incorporation ) of sp 90 reached a maximum level at 2 hours in all animals, and P-32 -labeling in Y/AL was significantly increased over O/AL and O/CR with an intermediate level found in O/CR animals. The turnover rate (phosph orylation/dephosphorylation) of sp 90 induced by BL was significantly suppressed and temporarily extended in O/AL as compared with O/CR, whi ch implied that CR not only increased incorporation of sp 90, but also enhanced a utilization of the phosphate pool very similar to that see n in Y/AL animals.