Acute hypoosmolality attenuates the suppression of cutaneous vasodilation with increased exercise intensity

Abstract

We examined the hypothesis that elevation of the body core temperature threshold for forearm skin vasodilation (TH(FVC)) with increased exercise intensity is partially caused by concomitantly increased plasma osmolality (P(osmol)). Eight young male subjects, wearing a body suit perfused with warm water to maintain the mean skin temperature at 34 +/- 1 degree C (ranges), performed 20-min cycle-ergometer exercise at 30% peak aerobic power (VO2(peak)) under isoosmotic conditions (C), and at 65% VO2(peak) under isoosmotic (H(EX)I(OS)) and hypoosmotic (H(EX)L(OS)) conditions. In H(EX)L(OS), hypoosmolality was attained by hypotonic saline infusion with DDAVP, a V2 agonist, before exercise. P(osmol) (mosmol/kg H2O) increased after the start of exercise in both H(EX) trials (P < 0.01) but not in C. The average P(osmol) at 5 and 10 min in H(EX)I(OS) was higher than in C (P < 0.01), whereas that in H(EX)L(OS) was lower than in H(EX)I(OS) (P < 0.01). The change in TH(FVC) was proportional to that in P(osmol) in every subject for three trials. The change in TH(FVC) per unit change in P(osmol) (deltaTH(FVC)/deltaP(osmol), degrees C x mosmol(-1) x kg H2O(-1)) was 0.064 +/- 0.012 when exercise intensity increased from C to H(EX)I(OS), similar to 0.086 +/- 0.020 when P(osmol) decreased from H(EX)I(OS) to H(EX)L(OS) (P > 0.1). Moreover, there were no significant differences in plasma volume, heart rate, mean arterial pressure, and plasma lactate concentration around TH(FVC) between H(EX)I(OS) and H(EX)L(OS) (P > 0.1). Thus the increase in TH(FVC) due to increased exercise intensity was at least partially explained by the concomitantly increased P(osmol).

Different vascular responses in glabrous and nonglabrous skin with increasing core temperature during exercise

“…20 and 30% Ex) was not enough for a statistical analysis because of the small increase in core temperature during the exercise. Mitono et al (2005) have reported that the T es threshold for forearm vasodilation measured using venous occlusion plethysmography was signiWcantly higher during 60% VO 2peak than 30% VO 2peak under isoosmotic conditions. Thus it is possible that plethysmography can sensitively detect the eVect of exercise on the T es threshold, but the blood Xow obtained from plethysmography includes blood Xow in both muscle and skin.…”

“…Cutaneous vasomotor response during the exercise is inXuenced by factors other than core body and skin temperatures. Central motor command, changes in mechano-receptor and metabo-receptor activities in muscles, changes in osmoreceptor activity, and some others have been proposed as nonthermal factors (Christensen et al 1942;Johnson 1986;Johnson and Park 1982;Kondo 1999;Mitono et al 2005). It is considered, therefore, that nonthermal factors occurring with exercise increased in an intensity-dependent manner adrenergic vasoconstrictor activity in the glabrous skin.…”

Osmotic Stress-induced Phosphorylation of H2AX by Polo-like Kinase 3 Affects Cell Cycle Progression in Human Corneal Epithelial Cells

“…Changes of the extracellular osmotic pressure are often found in some pathologic conditions, such as diabetes mellitus, uremia, dehydration after exercise, heat shock, fatal burns, and inflammation sites in various tissues including the cornea (1)(2)(3)(4). It has been shown that persistent hyperosmotic stress can induce DNA damage, cell cycle arrest, and apoptosis (5,6).…”

Body Temperature Regulation During Exercise and Hyperthermia in Diabetics

“…The increased T es thresholds at a given increase in P osm during exercise were identical to those during resting passive heat stress [23]. Mitono et al [24] supported this evidence by indicating that when the increase in P osm during exercise was attenuated by hypotonic saline infusion prior to exercise, the delayed onset of cutaneous vasodilation in response to increased T es during exercise was normalized. It has been suggested that the response of the thermoregulatory center was attenuated by plasma hyperosmolality via osmoreceptors.…”