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Alterations in glomerular and tubular dynamics at 1 and 14 days simulated microgravity and after acute return to orthostasisHead-down tilt (HDT) is utilized to simulate microgravity and produces a cephalad fluid shift, which results in alterations in fluid and electrolyte balance. These changes in volume homeostasis are due, in part, to alterations in multiple volume control mechanisms in which renal function is a major participant. We have previously demonstrated that glomerular filtration rate increases early in HDT and eventually returns to values not different from non-tilt measurements. This early increase in glomerular filtration rate was also demonstrated during days 2 and 8 of the SLS-1 mission. However, urine flow and electrolyte excretion does not parallel the alternations in glomerular filtration rate and the site of this change in nephron fluid reabsorption pattern has not been previously examined. Through determination of the location of alterations in tubular fluid reabsorption within the nephron, a more detailed hypothesis can be forwarded as to which specific neuro-humoral agents participating in control or renal function in microgravity conditions. the importance of this type of examination is that measurements in circulating neuro-humoral agents and urinary excretion patterns alone are not accurate predictors of how renal functional response may alter to head-down tilt or other models of simulated weightlessness. To examine this issue, renal micropuncture techniques were utilized in Munich-Wistar rats submitted 24 hour and 14 day head-down tilt, measuring all the determinants of glomerular ultrafiltration and obtaining data regarding segmental tubular fluid reabsorption. Following these measurements, the rats were returned to an orthostatic position and after 60 minutes, the measurements were repeated.
Document ID
19960021687
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Tucker, Bryan J.
(Physiology/Pharmacology Consulting San Diego, CA United States)
Mendonca, Margarida M.
(Physiology/Pharmacology Consulting San Diego, CA United States)
Date Acquired
August 17, 2013
Publication Date
January 1, 1995
Publication Information
Publication: Journal of Gravitational Physiology, Volume 2, No. 1
Subject Category
Aerospace Medicine
Accession Number
96N24962
Funding Number(s)
CONTRACT_GRANT: NAG2-659
CONTRACT_GRANT: NCC2-556
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
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