TISSUE-SPECIFIC DIFFERENCES IN HEAT-SHOCK PROTEIN HSC70 AND HSP70 IN THE CONTROL AND HYPERTHERMIC RABBIT

The ability to resolve protein members of the hsp70 multigene Family b y two-dimensional Western blotting permitted the characterization of a ntibodies which were specific in discriminating constitutively express ed hsc70 isoforms from stress-inducible hsp70 isoforms. This antibody characterization demonstrated that basal levels of hsp70 isoforms were present in the cerebellum of the control rabbit and that these were e levated following hyperthermia, whereas levels of hsc70 were similar i n control and hyperthermic tissue. Multiple isoforms of hsp70 were det ected but tissue-specific differences were not apparent in various org ans of the rabbit. However, species differences were observed as fewer hsp70 isoforms were noted in rat and mouse. In the control rabbit, hi gher levels of hsc70 protein were present in neural tissues compared t o non-neural tissues. Following physiologically relevant hyperthermia, induction of hsp70 was greatest in non-neural tissues such as liver, heart, muscle, spleen, and kidney compared to regions of the nervous s ystem. These studies suggest that the amount of preexisting constituti ve hsc70 protein may influence the level of induction of hsp70 in the stress response. Given this observation, caution is required in the em ployment of hsp70 induction as an index of cellular stress since endog enous levels of hsc70, and perhaps hsp70, may modulate the level of in duction. (C) 1997 Wiley-Liss, Inc.