Differential basal synthesis of Hsp70/Hsc70 contributes to interindividualvariation in Hsp70/Hsc70 inducibility

The source of intraspecies variation ih the expression of heat shock protei ns (HSPs) remains unresolved but could shed light on differential stress to lerance and disease susceptibility. This study investigated the influence o f variable basal HSP synthesis on differential inducibility of HSP synthesi s. Basal and heat-induced synthesis of the major HSP families in peripheral blood monocytes from healthy donors (n = 42) were analysed using biometabo lic labelling and densitometry. Basal Hsp70/Hsc70 synthesis and percentage induction of Hsp70/Hsc70 synthesis were significantly correlated (r = - 0.5 7, p < 0.0001), and described most accurately by an exponential decay equat ion (R = 0.68, R-2 = 0.46). This regression equation suggests that increasi ng levels of basal Hsp70/Hsc70 synthesis are accompanied by an exponential decrease in the percentage induction of Hsp70/Hsc70 synthesis. The model fi ts data from European and non-European population groups independently, alt hough both coefficients in the regression equation were larger for non-Euro peans. This implies population group as an additional factor influencing di fferential HSP expression. The differential inducibility of Hsp70/Hsc70 due to variable basal synthesis of Hsp70/Hsc70 and based upon population group may contribute to differential stress tolerance or disease susceptibility.