The impact of environmental factors on hypertension depends to a certain extent on the individual's genetic background. Environmental temperature is one of the known modulators of blood pressure. We have previously demonstrated abnormal expression of a major environmentally-controlled gene, hsp70, in hypertensive mice and rats. We have developed a simple ex vivo method for the evaluation of hsp genes expression in humans. In the present study, we investigated the accumulation of hsp70 mRNA in lymphocytes from normotensive and hypertensive humans. The data showed a higher accumulation of hsp70 mRNA in lymphocytes from hypertensives vs normotensives (2.04 +/- 0.35 vs 1.48 +/- 0.29 OD mm2, P < 0.05) submitted to heat stress (15 min at 42 degrees C). Basal levels were the same in both groups (0.11 +/- 0.01 vs 0.10 +/- 0.01 OD mm2, respectively). These results support our hypothesis that alterations in the expression of a major environmentally-controlled gene, hsp70, may be involved in enhanced environmental responses even in human hypertension.