Body temperature and plasma prolactin and norepinephrine relationships during exercise in a warm environment: effect of dehydration

1439-6327

Plasma prolactin ; Plasma norepinephrine ; Body temperature ; Exercise ; Dehydration

Springer Online Journal Archives 1860-2000

Medicine

Summary The effects of euhydration (Eh) and light (Dh1) and moderate (Dh2) dehydrations on plasma prolactin (PRL) levels were studied in 5 young male volunteers at rest and during exercise to exhaustion (50% of $$\dot V_{{\text{O}}_{{\text{2}} {\text{max}}} } $$ ) in a warm environment (Tdb=35° C, rh=20–30%). Light and moderate dehydrations (loss of 1.1 and 1.8% body respectively) were obtained before exercise by controlled hyperthermia. Compared to Eh, time for exhaustion was reduced in Dh1 and Dh2 (p〈0.01) and rectal temperature (Tre) rose faster in Dh2 (p〈0.05). Both venous plasma PRL and norepinephrine (NE) increased during exercise at any hydration level (p〈0.05). Plasma PRL reached higher values after 40 and 60 min in Dh2 and Dh1 (p〈0.05). Plasma NE values were higher in Dh2 at rest and at the 40th min during exercise (p〈0.05). Plasma PRL was linearly correlated to Tre and plasma NE (p〈0.001) but unrelated to plasma volume variation and osmolality. Our results provide further evidence for the major effect of body temperature in exercise-induced PRL changes. Moreover, the plasma PRL-NE relationship suggests that these changes may result from central noradrenergic activation.

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