SPECIES-SPECIFIC AND TISSUE-SPECIFIC SYNTHESIS PATTERNS FOR HEAT-SHOCK PROTEINS HSP70 AND HSP90 IN SEVERAL MARINE TELEOST FISHES

Using metabolic (in vivo) labeling methods and immunoblotting (Western) analysis, we determined the threshold induction temperature for enhanced synthesis of heat-shock proteins (HSP70 and HSP90) and the constitutive levels of these two classes of HSPs, respectively in brain, gill, and liver of four species of marine teleost fishes acclimatized to a common temperature (10 degrees C). For a given tissue of a species and among tissues of a species, little variation was found in HSP induction temperatures. However, among tissues of a species, the constitutive levels of HSPs differed substantially. Among species, wide variation was found in induction temperature (up to 8 degrees C when averaged for all tissues) and HSP concentration (greater than 10-fold differences for a single tissue). These results, obtained by analysis of animals from natural populations, contradict many of the assumptions, based largely on in vitro studies of isolated cells and tissues, about the dependence of the HSP threshold induction temperature and HSP concentrations on the previous acclimatization temperature. The wide variation in the HSP threshold induction temperatures among the different species and the wide variation in constitutive HSP levels among and within species may reflect, in addition to recent thermal exposure, the thermal history of the species during its evolution and the occurrence in the individual's habitat of other stressors that, like temperature, are capable of activating the heat-shock (stress) response.