Subject: Diet restriction and exercise influence Pb+2 distribution
S. Han et al., report a nice study in the Aug. '99 issue of Environ. Health
Perspect. (vol. 107, p. 657). Rats dosed with lead and then subjected to
(20% or 40%) caloric restriction or exercise (swimming) to induce weight
loss had greater levels of lead in systemic organs and blood. However, a
significant drop of lead in the bone compartment was not observed. The
authors speculate that only small amounts of bone Pb need be mobilized in
order to account for the elevated tissue levels of Pb in the exercising and
calorie-restricted animals. Alternatively, the existing Pb could have been
selectively retained or mobilized from soft tissues or other stores (fat?).
Interestingly, rats that lost weight by exercise had lower tissue levels of
lead in comparison to calorie-restricted rats.
Could this result mean that exercise-induced weight loss somehow mobilizes
less toxicants in comparison to reduced food intake (in humans, too)? If
so, what is the mechanism? More importantly, did the weight-loss induced Pb
increases in tissues result in any significant or additional toxicity (or
is weight-loss induced toxicity an urban myth)? I am still looking for
actual references (in the peer-reviewed literature, please) for similar
studies on lipophilic toxicants like DDT, other pesticides, PCBs, and TCDD.
Best of results,
Dr. Charles A. Miller III, rellim at mailhost.tcs.tulane.edu
Dept. Environmental Health Sciences, SL29
Tulane-Xavier Center for Bioenvironmental Research and
Tulane Univ. School of Public Health and Tropical Medicine
1430 Tulane Ave.
New Orleans, LA 70112
(504)585-6942, fax (504)584-1726
Bionet.toxicology newsgroup: http://www.bio.net/hypermail/TOXICOLOGY