The osmotic thresholds for thirst and vasopressin release are similar in healthy man

Abstract

The relationship between thirst perception and plasma osmolality was studied during hypertonic and physiological saline infusion in ten healthy volunteers. Thirst perception was quantified using a linear visual analogue scale which volunteers marked at intervals during the infusion periods. Infusion of hypertonic saline caused a steady rise in plasma osmolality together with a progressive linear increase in thirst perception and also plasma arginine vasopressin. No significant changes in thirst, plasma osmolality or plasma arginine vasopressin occurred during infusion of physiological saline. Linear regression analysis of the results defined the functions. Thirst (cm) = 0.3 (plasma osmolality-281) (r = +0.92, P less than 0.001) and plasma arginine vasopressin (pmol/l) = 0.4 (plasma osmolality-285) (r = +0.96, P less than 0.001). The osmolar threshold for thirst onset thus defined (281 mosmol/kg) was much lower than in previous studies and similar to the theoretical osmolar threshold for vasopressin release (285 mosmol/kg). We conclude that thirst perception rises in a progressive fashion throughout a wide range of plasma osmolality and that the osmolar threshold for thirst onset is similar to the theoretical osmolar threshold for vasopressin release. The results are compatible with the concept of either a single osmoreceptor subserving both thirst and vasopressin release, or two osmoreceptors sharing similar functional characteristics.

Effect of increased plasma osmolality on cold-induced thirst attenuation

“…Typically as P osm increases, plasma arginine vasopressin and thirst increase. This relationship has been illustrated in numerous studies (Greenleaf 1992;O'Brien et al 1998;Phillips et al 1985;Stricker et al 2002;Thompson et al 1986). However, changes in central volume have been shown to alter this relationship between thirst and P osm .…”

“…In the present study, cold exposure again resulted in an attenuation of thirst. A strong relationship has been reported between P osm and thirst sensations and between P osm and plasma arginine vasopressin (Phillips et al 1985;Thompson et al 1986). Typically as P osm increases, plasma arginine vasopressin and thirst increase.…”

“…Accordingly, a decrease in plasma volume would lower the osmotic threshold, while an increase in plasma volume would elevate the osmotic threshold. Given the strong relationship between thirst and plasma arginine vasopressin (Thompson et al 1986), it is reasonable to assume that changes in plasma volume have the same eVect on thirst. In the present study we speculate that an increase in central volume resulted in a decline in thirst sensation evidenced in the DH + P and EU + P treatments after cold exposure, despite an elevated P osm in the DH + P treatment.…”

The Effects of High-Intensity Intermittent Exercise Compared With Continuous Exercise on Voluntary Water Ingestion

“…77 4 78 Despite the known effect of HIIE on the rise in serum osmolality and an increase in 79 vasopressin release the effect on subsequent voluntary water intake is unknown. A rise in 80 osmolality above the vasopressin release threshold of approximately 285 mOsmol.kg -1 81 (Thompson, Bland, Burd, & Baylis, 1986) will lead to maximal anti-diuresis, resulting in an 82 osmotically driven thirst signal, thus facilitating water intake. Following a bout of HIIE, 83 increased serum osmolality above values experienced following continuous exercise of 84 matched work, may result in a greater osmotic signal, ultimately leading to increased water 85 intake.…”

“…403 404 Prior to the onset of thirst stimulated water intake, vasopressin is released to increase water 405 reabsorbtion in the kidneys (Bankir, 2001). Vasopressin release will increase until maximum 406 anti-diuresis has been reached (Thompson et al, 1986). In the current study there was a large 407 increase in plasma vasopressin concentration following the high intensity exercise when 408 serum osmolality values were above the reported threshold value.…”