We have previously shown in rats (Rattus norvegicus, Sabra strain) that during heat stress (at 41°C), upon heat- acclimation decline, HSP72 maintained heat-acclimatory protein levels despite of the transition to normothermic ambient temperature (at 24 °C). Both basal and heat stress hsp transcripts were profoundly higher than those measured during heat acclimation (continuous exposure at 34 °C, Tetievsky et al., 2008). Increased hsp mRNA/HSP72 protein ratio promoted the hypothesis that dynamic changes in mRNA are responsible for HSP72 proteo-stasis. To test this hypothesis, given that Eif2α is associated with initiation of translation, we measured during 15d and 30d of acclimation decline vs. acclimation: (i) the levels of Eif2α and its phosphorylated form, (ii) the effect of Eif2α dephosphorylation inhibition (using Sal 003, TOCRIS Cat No. 3657) on hsp 72 and 27 transcripts and the encoded HSPs. Our data demonstrated that heat acclimation induced increased Eif2α protein level with decreased phosphorylation. With acclimation decline, Eif2α-phosphorylation gradually increased. Basal and heat-stressed hsp 72 transcripts were elevated whereas HSPs levels were stable, suggesting HSPs proteo-stasis. Daily SAL administration (IP 0.1mg/kg b wgt) during acclimation decline elevated profoundly (vs. non SAL administered groups) hsp 72 transcripts and the mRNA/protein ratio under both basal and heat stress conditions, thus confirming our hypothesis on the importance of mRNA dynamics in HSPs adjustment during heat acclimation decline.