The impact of increased blood lactate on serum S100B and prolactin concentrations in male adult athletes.

S100B is an astroglial protein that is increased in the peripheral bloodstream after traumatic brain injury (TBI). Elevated serum levels of S100B have been shown to be predictive of mild TBI. Furthermore, physical activity (PA) can affect S100B levels. Interestingly, increased serum S100B concentrations have been detected in athletes without apparent TBI. Such increases could be attributed to tissue hypoperfusion reflected by blood lactate concentrations [BLa(-)] and/or increased serotonergic activity reflected by prolactin (PRL). The impact of increased blood lactates on peripheral S100B levels per se are yet unknown. The purpose of our study was to investigate if increased blood lactate induced by sodium lactate infusion, without the "side effects" of PA, resulted in changes in serum S100B and PRL. Twelve male adults were given a sodium lactate infusion for a period of 24 min by a perfusor with an infusion rate of 0.01 mL kg(-1) min(-1), increased every 3 min. The main outcome measures showed no increase in serum S100B (p > 0.05). Prolactin increased significantly (p < 0.05) after [BLa(-)] exceeded a concentration of 4 mmol L(-1). Furthermore, the expected values of blood lactate achieved peak values ranging from 11 to 15 mmol L(-1). We conclude that neither increased blood lactate nor serum PRL play an exclusive role in the regulation of S100B. Nevertheless, PA should be surveyed in medical history and critically assessed in determining the severity of TBI, especially in sports. Further studies are needed to clarify the impact of PA on the biomarker S100B.