The increase in urine osmolality in all races (R1-R4) might be due to an increase in water permeability in the kidney, matching the fact that athletes urinated less frequently [2]. This could lead to impairments of free water excretion in R1, R2 and R4 with indicators of a more chronic than an acute dehydration. Post-race symptoms reported by finishers in all races indicated this hypothesis. Glomerular filtration race significantly decreased and urine osmolality increased and it seemed to be a result in a change in renal function. Arginine vasopressin secretion, aldosterone activity and the prevalence of EAH SIADH

is also considered as a potentional SC75741 price mechanism to develop EAH [39], because arginine vasopressin (AVP) regulates body’s retention Emricasan of water. Changes in sodium and potassium concentrations and osmolality in plasma and urine are also indirect markers for the activity of aldosterone [2, 4, 16, 19, 45] and AVP-secretion [12, 42, 43, 45, 57, 59]. Urine [K+] significantly increased in R1 and R4, and urine specific gravity was associated with post-race urine [K+] in R4. On the contrary, urine [K+] in R2 and R3 remained stable, and urine [Na+] significantly

decreased in R2 and R3, although the K+/Na+ ratio in urine was < 1 only in R3. The increased urinary [Na+] losses could be compatible with SIADH in R2 and R3. In all races, the transtubular potassium gradient increased and was > 10 in R1, R3 and R4, probably due to an increased aldosterone activity. This change in aldosterone is associated with a change in the K+/Na+-ratio in urine, a positive ratio suggests an increased aldosterone activity [16, 18]. In all races (R1-R4), the K+/Na+-ratio in urine increased. The K+/Na+-ratio in urine was < 1.0 only in R3, suggesting Florfenicol that more potassium

than sodium was excreted through the kidney, however the K+/Na+-ratio in urine was > 1 in R1, R2 and R4. Body water increase with simultaneous dehydration (R2-R4) might be possibly due to endocrine-induced renal water retention, in order to maintain the metabolic processes that are required for energy supply and blood flow during prolonged exercise [54]. Finishers were more hyperhydrated than dehydrated in R3. Apart from fluid overload, however, other mechanisms may have lead to water retention in R3, such as protein catabolism [54]. In a 24-hour running race, Fellmann et al. [59] found an increase in plasma volume, aldosterone and AVP. Stuempfle et al. [24] showed an increased activity of both aldosterone and AVP after an ultra-endurance race. Alternatively, there might be also an impairment in mobilization of osmotically-inactive sodium stores or inappropriate inactivation of osmotically-active sodium [11, 18]. These Selleckchem PD-1 inhibitor cannot be determined from the present study. Fluid overload and the prevalence of EAH Fluid overload is considered as the main risk factor for EAH [39, 48].