Bicarbonate reduces serum prolactin increase induced by exercise to exhaustion

PURPOSE: The aim of the study was to examine the effect of acid-base status on serum prolactin (PRL) concentration postexercise.

METHODS: Seven male recreational athletes participated in two experimental trials separated by 1 wk. In the respective trial, subjects received either a placebo infusion (normal isotonic saline) or an alkali infusion (isotonic sodium bicarbonate) before and during exercise. Venous and capillary blood samples were drawn at rest, immediately after a 10-min warm-up period, and after a maximal ramp test on a cycle ergometer, as well as at 3, 6, 10, and 15 min postexercise.

RESULTS: Power output, HR, capillary blood lactate concentration, carbon dioxide pressure (PCO2), and partial oxygen pressure (PO2) did not differ between trials at any point in time. Capillary PO2 did not change from resting values, but a significant increase (P < 0.05) was found from the end of warm-up to 3 min of the recovery period. Exercise induced a significant (P < 0.01) decrease in capillary blood bicarbonate concentration (HCO3-), pH, base excess (BE), and PCO2 at exhaustion and during the recovery period. Significantly higher HCO3-, pH, and BE were found during bicarbonate infusion and postexercise in comparison with the placebo trial. Serum PRL concentration was significantly increased 3 min postexercise until the end of the placebo trial, whereas after bicarbonate infusion, serum PRL concentration did not change from values at rest. Significant (P < 0.01) differences between trials in serum PRL concentration were found 10 and 15 min postexercise.

CONCLUSIONS: The present study suggests that acidosis is a stimulus for exercise-induced PRL secretion.