Body Fluid Changes, Cardiovascular Deconditioning and Metabolic Impairment Are Reversed 24 Hours after a 5-Day Dry Immersion

Abstract

Dry immersion is an effective and useful model for research in physiology and physiopathology. The focus of this study was to provide integrative insight into renal, endocrine, circulatory, autonomic and metabolic effects of dry immersion. We assessed if the principal changes were restored within 24 h of recovery, and determined which changes were mainly associated with immersion-induced orthostatic intolerance. Five-day dry immersion without countermeasures, and with ad libitum water intake, standardized diet and a permitted short daily rise was performed in a relatively large sample for this experiment type (14 healthy young men). Reduction of total body water derived mostly from extracellular compartment, and stabilized rapidly at the new operating point. Decrease in plasma volume was estimated at 20% -25%. Five-day immersion was sufficient to impair metabolism with a decrease in glucose tolerance and hypercholesterolemia, but was not associated with pronounced autonomic changes. Five-day immersion induced marked cardiovascular impairment. Immediately after immersion, over half of the subjects were unable to accomplish the 20-min 70˚ tilt; during tilt, heart rate and total peripheral resistance were increased, and stroke volume was decreased. However, 24 hours of normal physical activity appeared sufficient to reverse orthostatic tolerance and all signs of cardiovascular impairment, and to restitute plasma volume and extracellular fluid volume. Similarly, metabolic impairment was restored. In our study, the major factor responsible for orthostatic intolerance appeared to be hypovolemia. The absence of pronounced autonomic dysfunction might be explained by relatively short duration of dry immersion and daily short-time orthostatic stimulation.

Pain and Vertebral Dysfunction in Dry Immersion: A Model of Microgravity Simulation Different from Bed Rest Studies

“…Although several factors may influence plasma volume, the decrease of 17% seen in the present study is comparable to that observed in space [19, 27]. Furthermore, results about blood changes in DI have been observed [26].…”

Intervertebral Disc Swelling Demonstrated by 3D and Water Content Magnetic Resonance Analyses after a 3-Day Dry Immersion Simulating Microgravity

“…Recent studies favor a poro-elastic behavior model of the IVD explaining in and out fluid flow in relation to loading (Vergroesen et al, 2016). In our study, plasma volume and osmolarity variations suggest out-flow of water during loading (Coupé et al, 2013). Therefore, our IVD volume results would validate the mechanical hypothesis that a decrease in hydrostatic pressure leads to a fluid transfer into the IVD.…”

Participation of NO-synthase in Control of Nitric Oxide Level in Rat Hippocampus after Modelling of Ischaemic and Haemorrhagic Insult

“…This result is extremely important and a possible explanation for this fact was obtained in the electrophysiological experiments. Such development indicates a violation of the conditions of interneuron communications and disrupting the input-output processes at the level of individual neurons and their populations at lower oxygen tension in the tissues of the hippocampus, which controls processes of storage and organisation of the behaviour (Coupé et al 2013, Kulchitsky et al 2014, Roch et al 2007). The short-term effect of increasing the amplitude of excitatory postsynaptic potentials and population spikes on the output signal level can be explained by the development of excitotoxicity, with the release of excitatory amino acids.…”

“…However, the extent to which the initial cellular injury contributes to propagation of the inflammatory response and further tissue damage is poorly understood. In the experiments, we modelled the ischaemic stroke and haemorrhagic stroke (Coupé et al 2013, Kulchitsky et al 2014, Roch et al 2007. As the used method of applying a spin trap places some limitations on the experimental protocol, such as the need to wait for 30 minutes for the accumulation signal, we have not included in the research the short interval (up to 3 hours) from the beginning of the ischaemia.…”

“…Animals were kept in standard vivarium conditions (12/12-light and dark rhythm, air temperature of 23±1°C and stable supply and exhaust ventilation) with free access to water and food (ad libitum) and a diet in accordance with the standards for keeping laboratory animals. For the modelling of ischaemic stroke, animals were subjected to 5-minute hypoxia (conditional rise to a height of 4500m above sea level which corresponded to a pressure of 432mmHg and a decrease in oxygen partial pressure pO from 159mmHg to 90mmHg on average) (Coupé et al 2013, Kulchitsky et al 2014). After 5, 24 and 72 hours, it was carried out fence of the hippocampus.…”