title: Changes in organ perfusion and weight ratios in post-simulated microgravity recovery.
abstract: Head-down tilt models have been used as ground-based simulations of microgravity. Our previous animal research has demonstrated that there are significant changes in fluid distribution within 2 h after placement in a 45 degrees head-down tilt (45HDT) position and these changes in fluid distribution were still present after 14 days of 45HDT. Consequently, we investigated changes in fluid distribution during recovery from 16 days of 45HDT. Changes in radioactive tracer distribution and organ/body weight ratio were examined in rats randomly assigned to a 45HDT or prone control group. The 45HDT rats were suspended for 16 days and then allowed to recover at the prone position 0, 77, 101, or 125 h post-suspension. Animals were injected with technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, MW=492 amu, physical half-life of 6.02 h) and then killed 30 min post-injection. Lungs, heart, liver, spleen, kidneys, and brain were harvested, weighed, and measured for radioactive counts. Statistical analyses included two-way analysis of variance (ANOVA) that compared 45HDT versus controls at the four experimental time points. The organ weight divided by the body weight ratio for the brain, heart, kidneys and liver in the 45HDT rats was significantly different than the control rats, regardless of time (treatment). There was no difference between the different time points (time). The average 99mTcDTPA count divided by the organ weight ratio values for the heart, liver, and spleen were significantly higher in the 45HDT group than the control group. The average counts for the heart and spleen were significantly higher at 77, 101, and 125 h than at time zero. We conclude that the major organs have different recovery patterns after 45HDT for 16 days in the rat.
authors.affiliation: The Joan B. and Donald R. Diamond Lung Injury Laboratory, Department of Pediatrics and Steele Memorial Children's Research Center, University of Arizona College of Medicine, Tucson, Arizona 85724, USA.
authors.forename: Daniel B
authors.initials: DB
authors.lastname: Deever
authors.forename: Robert S
authors.initials: RS
authors.lastname: Young
authors.forename: Shengjun
authors.initials: S
authors.lastname: Wang
authors.forename: Beth A
authors.initials: BA
authors.lastname: Bradshaw
authors.forename: Jonathan
authors.initials: J
authors.lastname: Miles
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Pettis
authors.forename: Mark L
authors.initials: ML
authors.lastname: Witten
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001921:Brain / Q000033:anatomy & histology / Q000502:physiology; D018495:Fluid Shifts / Q000502:physiology*; D018475:Head-Down Tilt; D006321:Heart / Q000033:anatomy & histology / Q000502:physiology; D007668:Kidney / Q000033:anatomy & histology / Q000502:physiology; D008099:Liver / Q000033:anatomy & histology / Q000502:physiology; D008168:Lung / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D009929:Organ Size; D051381:Rats; D011916:Rats, Inbred F344; D013154:Spleen / Q000033:anatomy & histology / Q000502:physiology; D014781:Viscera / Q000033:anatomy & histology / Q000502:physiology*; D018474:Weightlessness Simulation