Sex-related differences in sweat gland cholinergic sensitivity exist irrespective of differences in aerobic capacity

Abstract

Mechanisms accounting for sex-related differences in the sweat response remain to be elucidated. In the present study, we focused on differences in sweat gland cholinergic sensitivity between males and females. Since, males usually possess higher aerobic capacity than females, we investigated sweating in males and females grouped according to aerobic capacity (.VO(2peak)). Forty-four subjects were assigned to four groups: males with higher (MH) and lower (ML), and females with higher (FH) and lower (FL) .VO(2peak). Forearm sweating was induced by iontophoretic administration (1.5 mA, 60 muA cm(-2), 5 min) of pure water or varying concentrations of pilocarpine hydrochloride (0.125, 0.250, 0.5, 1.0 and 2.0%). Local sweat rate (absorbent paper) and the number of activated sweat glands (iodine impregnated paper) were computed. Maximal pilocarpine-induced sweat rate (SR(max)) and the pilocarpine concentration which elicited 50% of maximal sweating response (K (m)) were calculated. Sweat rate and active gland density increased in response to greater doses of pilocarpine (p < 0.05). Inter-group differences were evident: SR(max) was greatest for MH and lowest for FL (p < 0.05), but no significant differences were observed between ML and FH (p = 0.24). Higher SR(max) were observed, within-sex, for those with greater aerobic capacity (p < 0.05). Furthermore, males' K (m) values were higher than females', indicating greater sweat gland affinity for pilocarpine even for groups having similar aerobic capacity (p < 0.05). In summary, we confirmed that the human sudomotor response is affected by aerobic capacity but, also, that sex-related differences in sweat gland cholinergic sensitivity exist and are not necessarily associated with the typical differences in .VO(2peak) observed between sexes.

Sex differences in postsynaptic sweating and cutaneous vasodilation

“…In contrast, Buono and Sjoholm (2) observed a similar sweat rate to a given dose of pilocarpine between sexes with similar training status, albeit it was achieved through a greater sweat output in males, relative to greater sweat gland recruitment in females. Most recently, Madeira et al (21) reported that the extrapolated maximal sweat response to pilocarpine does not differ between males and females matched for maximum oxygen consumption, even though females demonstrate a lower cholinergic sensitivity of the sweat gland. Although these studies generally support peripheral differences in the properties of the sweat gland in females, the mechanisms by which sex differences in sudomotor activity occur for a given dose of cholinergic agonist have not been evaluated.…”

Autonomic thermoregulatory dysfunction in neurofibromatosis type 1

“…In a previous study applying the present method, healthy volunteers showed 20% reduced sweating response related to 20% reduced aerobic capacity 9 . Therefore, it seems unlikely that the 10% lower VO 2max previously reported in NF1 could exclusively explain the 35% to 65% reductions in NF1 SR observed here.…”

“…To prevent individual variations in local skin temperature, the forearm was heated for 15 minutes prior to pharmacological stimulation and its temperature was maintained (~35° C) throughout the experiment, using radiant heat from an adjustable infrared emission lamp (Quartz®, Brazil). It has been shown previously that these procedures induce maximal sweating to pilocarpine, irrespective of sex and aerobic capacity 9 . Sweat secretion was collected for 15 minutes just after stimulation using a 16 cm 2 absorbent paper (J Prolab, Brazil) placed inside a plastic chamber to prevent sweat evaporation.…”

“…The main human physiological mechanisms to dissipate metabolic heat consist of increased skin temperature, through cutaneous vasodilation and sweat production and vaporization, both simultaneously triggered by increased internal and skin temperatures. Individual characteristics may affect the magnitude of thermoregulatory responses, including sex, aerobic capacity, as well as the existence of any disease 6,8,9 . As an example, the neuropathy caused by progressive central demyelization in multiple sclerosis produces systemic failure in maintaining internal temperature during heat exposure due to decreased neural control of cardiovascular responses and impaired sweat function.…”

Antibiotic consumption and Enterobacteriaceae skin colonization in hospitalized adults

“…8 Both the groin and axilla are rich in sweat glands and this may explain why these sites are most frequently colonized, and why males, with more active sweat glands, are more commonly colonized. 9 The finding that colonization was higher for patients on antibiotics may relate to the effect of antibiotics on the skin microbiome. Alterations (loss) to the skin microbiome may reduce the resistance to colonization normally provided by commensal bacteria, so called colonization resistance.…”