Cross-talk between nitric oxide and HSP70 in the antihypotensive effect ofadaptation to heat

In this work, we evaluated the effect of adaptation to heat on the fall of blood pressure (BP) induced by heat shock (HS) and the interrelation betwee n nitric oxide (NO) and heat shock protein, HSP70. Experiments were carried out on Wistar rats. It was shown that I-IS resulted in a generalized and t ransient increase in NO production (the election paramagnetic resonance met hod) and a fall of BP from 113+/-3 to 88+/-1 mm Hg (p<0.05). Adaptation to heat itself did not affect BP, but completely prevented the NO overproducti on and hypotension induced by HS. The adaptation simultaneously increased t he brain NO-synthase content and induced HSP70 synthesis (the Western blot analysis) in various organs. Both the antihypotensive effects of adaptation and HSP70 accumulation were completely prevented by L-NNA. an inhibitor of NO synthesis, or quercetin, an inhibitor of HSP70 synthesis. The data sugg est that adaptation to heat stimulates NO synthesis and NO activates synthe sis of HSP70. HSP70, which hampers NO overproduction. thus restricts the BP fall induced by heat shock.