Hamilton. Effects of high altitude and water deprivation on arginine vasopressin release in men. Am J Physiol Endocrinol Metab 286: E20-E24, 2004. First published September 3, 2003 10.1152/ ajpendo.00332.2003.-High-altitude exposure changes the distribution of body water and electrolytes. Arginine vasopressin (AVP) may influence these alterations. The purpose of this study was to examine the effect of a 24-h water deprivation trial (WDT) on AVP release after differing altitude exposures. Seven healthy males (age 22 Ϯ 1 yr, height 176 Ϯ 2 cm, mass 75.3 Ϯ 1.8 kg) completed three WDTs: at sea level (SL), after acute altitude exposure (2 days) to 4,300 m (AA), and after prolonged altitude exposure (20 days) to 4,300 m (PA). Body mass, standing and supine blood pressures, plasma osmolality (P osm), and plasma AVP (PAVP) were measured at 0, 12, 16, and 24 h of each WDT. Urine volume was measured at each void throughout testing. Baseline P osm increased from SL to altitude (SL 291.7 Ϯ 0.8 mosmol/kgH 2O, AA 299.6 Ϯ 2.2 mosmol/kgH2O, PA 302.3 Ϯ 1.5 mosmol/kgH 2O, P Ͻ 0.05); however, baseline PAVP measurements were similar. Despite similar P osm values, the maximal PAVP response during the WDT (at 16 h) was greater at altitude than at SL (SL 1.7 Ϯ 0.5 pg/ml, AA 6.4 Ϯ 0.7 pg/ml, PA 8.7 Ϯ 0.9 pg/ml, P Ͻ 0.05). In conclusion, hypoxia appeared to alter AVP regulation by raising the osmotic threshold and increasing AVP responsiveness above that threshold.acute mountain sickness; antidiuretic hormone; dehydration; fluid regulation; osmotic threshold EXPOSURE TO HIGH ALTITUDES may lead to acute mountain sickness (AMS), which is considered an indication of poor acclimatization. One distinct characteristic of AMS normally seen at altitude is the lack of a diuresis (10,11,26). Arginine vasopressin (AVP) has been implicated in AMS (4, 10) because of its role in reducing free water excretion at the kidney and because of altitude-induced increases in plasma osmolality (3-5), decreases in plasma volume (7,22,25), and increases in blood pressure (5, 21, 28), the three primary determinants of AVP release (23,27,29).Previous research examining the AVP response to altitude, however, does not support a role for AVP in AMS, because different exposures (1,900-5,400 m) of varying durations (3-30 days) have shown no rise in plasma AVP (P AVP ) (16,18,22). The lack of a P AVP response is paradoxical when we consider that altitude significantly alters plasma osmolality (P osm ) (3-5). Only one study has shown an augmentation in P AVP (24), this in response to 7 days of exposure to 4,200 m. Ramirez and colleagues (17, 19), however, have shown that high-altitude natives (2,600 m) have greater resting P AVP than sea-level natives.Osmotic challenges to evaluate the AVP response at altitude normally take the form of salt infusion. Typical results have shown similar increases in P osm with no change in P AVP between altitude and sea level infusions (17,18,20). Bestle et al. (3) showed that 8 days of exposure to 4,559 m enhanced baseline P osm and decr...
This study examined the change in plasma volume (% delta PV) in response to consecutive Wingate tests (30 sec Anaerobic Power test). Twelve active men (21 +/- 1.6 yr, 81.3 +/- 6.6 kg) performed two Wingate tests (W1 and W2, separated by 10 min) on three occasions (T1-T3, tests were two weeks apart). Exercise resistance was maintained at 75 g.kg-1 body weight during testing. Blood samples were taken immediately before (Pre) and after (IP) W1 and W2. There were no significant differences in hematocrit, hemoglobin, mean power (MP) or peak power (PP) between T1-T3. There was a marked hemoconcentration in response to W1 (IP W1, -17.4 +/- 2.6% delta PV), with a further, but not significantly greater, hemoconcentration following W2 (IP W2, -8.2 +/- 1.1% delta PV). The % delta PV, between PRE W1 and IP W2 was-20.1 +/- 3.1%. These results suggest that an existing hemoconcentration (W1) may affect the magnitude of the % delta PV response to subsequent supramaximal exercise (W2).
The biochemical adaptations of different muscle fiber types to endurance training of various intensities and durations have previously been investigated. The objective of this study was to determine the effects of two different endurance training programs on muscle fiber morphology. Twenty-four male Sprague-Dawley rats were randomly assigned to three groups: high intensity/low duration endurance trained (HILD), low intensity/high duration endurance trained (LIHD), or untrained (controls). Following the twelve week training period, muscle fibers of the gastrocnemius muscle of the rats were histochemically classified as type I, type IIa, or type IIb following myosin ATPase staining with pre-incubation at pH 4.6. Muscle fiber type distribution and cross-sectional areas were then determined. Neither HILD nor LIHD rats demonstrated significant differences in fiber type distribution compared to controls. When all fiber types were pooled together and analyzed, there were no differences between the three groups with respect to fiber size. However, when the three fiber types were analyzed individually, HILD animals demonstrated a significant reduction in the size of type IIa fibers while LIHD rats experienced a significant diminution in the size of type I and type IIb fibers. Thus, the morphological adaptations of the muscle fibers in the HILD and LIHD groups were fiber type specific.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.