Effects of bromocriptine on sweat gland function during heat acclimatization.

This study examined the involvement of the hormones aldosterone and prolactin in sweat gland function during heat acclimatization. Two groups of male subjects (n = 8) were tested - one receiving a placebo (control), the other receiving bromocriptine. Both groups performed cycle ergometer exercise at 50% of maximal oxygen uptake over 10 consecutive days in an environmental chamber maintained at 39 degrees C and 30% relative humidity. Duration of exercise was 90 min on days 2-4 and 6-9, and 45 min on test days 1, 5 and 10. Electrolyte concentrations were determined by total body washdown. Prolactin increased (p less than 0.001) during exercise on day 1 in the control group but not on days 5 and 10. In contrast, prolactin was suppressed by bromocriptine and did not rise in response to exercise or heat exposure. Plasma aldosterone increased during exercise in both groups, showing no differences between groups. The sodium concentration in sweat decreased significantly (p less than 0.05) in the control group from day 1 to 10 but was unchanged in the treatment group. These data suggest that acclimatization-related changes in sweat gland function may be attenuated by increases in central dopaminergic activity and implicate prolactin in control of sweat gland function.