Oxidant/Anti-Oxidant Status in Rats Exposed to Simulated Weightlessness by Hind-Limb Unloading and Reloading

Abstract

Hindlimb suspension or better known as hind-limb unloading (HLU) of rats is a validated model representing weightlessness, simulating microgravity. This is accomplished by removal of weight-bearing loads from hindquarters producing a cephalic fluid shift. The current study examines whether exposure to microgravity by hind-limb unloading will activate oxidant/antioxidant defense system. Tissue levels of malondialdehyde (MDA), total glutathione (GSH+GS-SG) and superoxide dismutase (SOD) were measured in harvested tissues following HLU and reloading. To rule out any variability in normal dietary oxidant intake, all animals received in their diet Purina rat chow containing 9.6% soy meal (4.8% soy protein). Results show that tissues harvested from rats following 2 weeks of unloading had significantly elevated MDA levels ranging from 0.3-0.8 M/mg protein when compared to paired loaded controls (0.2-0.4μM/mg protein, p < 0.5). Tissues from rats reloaded for 2 weeks following unloading decreased MDA levels from their peak values (p<0.05). GSH levels increased up to 350 M depending on tissues as a result of unloading, and two weeks of reloading decreased GSH levels to 250 M from their peak levels. SOD levels increased in all harvested organs in unloaded group ranging from 0.8-4.0 M with continued increase after two weeks of reloading, p < 0.05). Our data indicate that oxidative stress is induced during unloading as evidenced by increased tissue MDA levels. The response involves an increase in GSH and SOD levels, but two weeks of reloading decreased MDA and GSH levels, while further increasing SOD levels, implying the tissue adaptation to induced oxidative stress. Daily Food Consumption 21.56 ± 2.75 gm Water Intake (ml/rat/day) 28.92 ± 0.27 versus Gr. II p < 0.05 versus Gr. III p < 0.05 Water Intake (ml/rat/day) 20.64 ± 1.91 versus Gr. III p < 0.05 Water Intake (ml/rat/day) 25.23 ± 3.60 p < 0.05, significant differences between the initial and final values.

Triticale Bran Alkylresorcinols Enhance Resistance to Oxidative Stress in Mice Fed a High-Fat Diet

“…Also, it is known that SOD is a strong antioxidant that out-competes the reactions of O 2 . − to protect the cell from its toxicity [39]. The supplementation of 0.5% antioxidants (ARs or VE) with a high-fat diet did not significantly enhance SOD activity.…”

“…Although the mechanism of action requires further investigation, it would be presumed that ARs help increase GSH levels by direct reduction of GSSG through hydrogen atom transfer/donation or by free radical quenching, which indirectly helps maintain higher GSH levels. Since GSH has multiple roles in the endogenous antioxidant defense system, it is likely that GSH cooperates with SOD in the removal of free radicals [39]. This may explain the significant effects demonstrated by ARs on GSH, yet less pronounced or undetectable effects on SOD activity in the liver and heart, respectively, as ARs may only impact SOD activity indirectly through GSH.…”

Animal model of simulated microgravity: a comparative study of hindlimb unloading via tail versus pelvic suspension

“…Tail‐HLS was conducted as described previously (Chowdhury and Soulsby ; Chowdhury et al. ) using a tail harness constructed by looping a strip of Skin‐Trac orthopedic foam (Zimmer Inc., Charlotte, NC) around a pulley that can travel along a bar traversing the length of the cage.…”

Pancreatic Histology and Associated Biochemical Changes in Rats on Hind-Limb Suspension

“…The details of the method have been reported earlier from our laboratory (Chowdhury and Soulsby, 2008). We have earlier demonstrated that hind-limb unloaded rats maintained on a normal Purina diet displayed elevated stress as evidenced by elevated MDA levels in brain tissue harvested after two weeks of suspension (Chowdhury et al, 2007).…”

“…The pancreata were extracted for measurements of malondialdehyde (MDA) and glutathione levels. Our preliminary studies (Chowdhury et al, 2007 andSoulsby, 2008) have demonstrated that HLS rats maintained on a normal Purina diet, displayed elevated malondialdehyde (MDA) and glutathione levels.…”