In response to heat shock five isoforms of hsp70 are accumulated in the myocardium of Wistar rats highly resistant to stress in comparison with only 3 isoforms of hsp70 in August rats with a lower resistance to stress. This suggests that genetic mechanisms which determine the stress resistance of a particular strain are probably related to transcription of hsp70 genes.Key Words: stress; heat shock; myocardium; hsp 70; genetic strains Different organisms from procaryotic to high eucaryotic react to environmental stress factors in different ways. At the same time a common feature of cell response to stress in many cases is quick synthesis of so-called heat shock proteins, hsp [13,15]. The main members of the above family are proteins with a molecular weight around 70 kD (hsp70). Hsp70 are known to participate in the restriction of stress-induced damage by disintegrating abnormal protein-protein interactions [13,15]. For instance, experiments on cell cultures from Drosophila melanogaster [1], Syrian hamster [9,10], and rat liver [6,7] have demonstrated a correlation between increased resistance to stress, namely to heat shock, and hsp70 accumulation. At ties [3,4,8,12]. Thus, the role of heat shock proteins in the formation of stress resistance of the organism remains unclear. One possible approach is the study of peculiarities of accumulation of hsp70 in response to a single stress factor in various animal strains with different resistance to stress.In this context the aim of the present study was, first, to compare quantitatively stress resistance in different animal strains by comparing their resistance to heat shock and, second, to evaluate the differences in the accumulation of hsp70 and their isoforms in response to heat shock in rats with different resistance to stress and to compare the differences in hsp70 accumulation with the differences in stress resistance. Rats of the Wistar and August strains were used.
MATERIALS AND METHODSExperiments were carried out on Wistar and August rats weighing 200-250 g. Heat shock reproduced after Currie et al. [2] was used as the stress influence. To this end the rats were first narcotized with Nembutal (50 mg/kg, i.p.) and then exposed to 80~ for 20 rain in a special incuba-
235in these parameters in LR rats, whose resistance to the oxygen deficit sharply increased, allow us to conclude that the first enzymatic complex of the respiratory chain, which helps regulate its activity, is of fundamental importance for the formation of the brain's resistance to hypoxia.
The use of two-dimensional electrophoresis to study the polypeptide composition of heat shock proteins 70 synthesized in the myocardium of Wistar and August rats in response to thermal stress and repetitive immobilization stress revealed interstrain differences in the composition of stimulated polypeptides in these proteins. The differences are mainly due to differential expression of the heat shock protein gene(s) encoding polypeptides with pI 6.2-6.0 in the two strains. The drastically reduced levels of the synthesis and/or accumulation of some heat shock proteins 70 in the hearts of August rats are associated with their failure to develop cardioprotective phenomena in response to repetitive immobilization stress.
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