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ARS Home » Plains Area » Grand Forks, North Dakota » Grand Forks Human Nutrition Research Center » Healthy Body Weight Research » Research » Publications at this Location » Publication #71334
Title: IMPAIRED STARTLE RESPONSE IN GROWING RATS MARGINALLY IRON-DEPLETED WITHOUT OVERT ANEMIA

Author
item Hunt, Janet
item Penland, James

Submitted to: Trace Elements in Man and Animals International Symposium
Publication Type: Proceedings
Publication Acceptance Date: 5/18/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Approximately 20% of US women of child-bearing age have low iron stores, as indicated by serum ferritin, although only a small proportion of these women have anemia, as indicated by low hemoglobin. Do such low iron stores impair normal health and function? We measured involuntary central nervous system responsiveness in rats that had been marginally iron depleted by consuming a low iron diet. Although such rats had substantially lower amounts of liver iron stores and serum iron, hemoglobin was reduced by only 7%, a change that would generally not be considered anemic. These animals were tested for the speed and magnitude of their normal physical reaction when startled with a sudden loud noise. Rats that were marginally depleted with iron were slower to react to the noise stimulus. Adding iron back into the diets of these animals partially improved both their iron stores and their reaction time. Further animal studies will be conducted to validate this initial observation. Startle response testing can be reliably conducted in human volunteers. If verified to be sensitive to marginal iron status, startle response results could serve as a useful functional indicator to help define optimal iron status in humans.

Technical Abstract: Startle response was investigated in growing animals after marginal dietary iron (Fe) depletion and subsequent, partial repletion. Weanling, female Sprague-Dawley rats were fed AIN-93G diets modified to contain 15 or 90 mg Fe/kg of diet (by analysis) for 53 d of Fe depletion, and 90 ug/kg for another 28 d of repletion. Six of 12 rats per group were killed for tissue analysis at the end of the depletion period. The other 6 were tested for startle response during the 12-hr dark cycle at the end of depletion and repletion, then killed. A total of 120 acoustic startle trials were administered in a counterbalanced manner, with an intertrial interval of 30 s (range 21-40 s). Fe-depleted reduced hemoglobin (142+/-7 vs 153+/-4 g/L, p < 0.01) (mean +/- SD, depleted vs controls), serum Fe (25+/-5 vs 40+/-5 umol/L, p < 0.01), and liver nonheme Fe (0.7+/-0.2 vs 5.5+/-1.4 umol/g dw, p < 0.01), without differences in hematocrit, Fe binding capacity, or brain Fe. Fe-depleted rats displayed greater startle response latency (14.4+/-0.5 vs 13.5+/-0.6 msec, p < 0.05), with no difference in response amplitude. Fe-repletion was only partly successful: repleted rats, compared with controls, had reduced hemoglobin (149+/-5 vs 157+/-5 g/L, p < 0.05) and liver nonheme Fe (4.0+/-0.6 vs 6.9+/-2.3 umol/g dw, p < 0.05), without differences in hematocrit, serum Fe, Fe binding capacity, or brain Fe. Response latency, although not completely corrected, was no longer significantly different in the repleted rats. Marginal Fe depletion impaired central nervous system reactivity. Startle response testing could be a sensitive functional indicator of marginal Fe status, with potential application to humans.