Effects of weight loss and exercise on the distribution of lead and essential trace elements in rats with prior lead exposure

We studied the effects of weight loss and non-weight-bearing exercise (swim ming) on blood and organ lead and essential metal concentrations in rats wi th prior lead exposure. Nine-week-old female Sprague-Dawley rats (n = 37) r eceived lead acetate in their drinking water for 2 weeks, followed by a 4-d ay latency period without lead exposure. Rats were then randomly assigned t o one of six treatment groups: weight maintenance with ad libitum feeding, moderate weight loss with 20% food restriction, and substantial weight loss with 40% food restriction, either with or without swimming. Blood lead con centrations were measured weekly. The rats were euthanized after a 4-week p eriod of food restriction, and the brain, liver, kidneys, quadriceps muscle , lumbar spinal column bones, and femur were harvested for analysis for lea d, calcium, copper, iron, magnesium, and zinc using atomic absorption spect rophotometry. Both swimming and nonswimming rats fed restricted diets had c onsistently higher blood lead concentrations than the ad libitum controls. Rats in the substantial weight loss group had higher organ lead concentrati ons than rats in the weight maintenance group. Rats in the moderate weight loss group had intermediate values. There were no significant differences i n blood and organ lead concentrations between the swimming and nonswimming groups. Organ iron concentrations increased with weight loss, but those of the other metals studied did not. Weight loss also increased hematocrits an d decreased bone density of the nonswimming rats. The response of lead stor es to weight loss was similar to that of iron stores because both were cons erved during food restriction in contrast to decreased stores of the other metals studied. It is possible that weight loss, especially rapid weight lo ss, could result in lead toxicity in people with a history of prior excessi ve lead exposure.