EFFECT OF LEAD-EXPOSURE ON PATTERNS OF FOOD-INTAKE IN WEANLING RATS

The reduction in growth resulting from lead (Pb) exposure in weanling rats is consistent with a lowering of the biological set-point for foo d intake. In this study the effects of lead on the patterns of food in take were examined. For 10 days (from ages 26 to 36 days), female rats were provided with drinking water containing 250 ppm lead as the acet ate (n = 6) or equivalent acetate as sodium acetate (n = 6). A compute rized system was used to monitor daily food intake at 5-min intervals over 10 successive 23-h periods (each period consisting of 12 h dark, 11 h light). Control rats consumed approximately 75% to 85% of their f ood intake during the dark phase. Exposure to lead resulted in decreas ed body weight, tail length, and cumulative food intake. Decreased foo d intake associated with lead during the first 6 days of exposure was due to a decrease in the size of each meal during the dark phase, whic h reflected a decrease in the duration of each meal. These results sug gest that lead, at least initially, was affecting food-satiety signals to produce a premature termination of food intake during a meal. Afte r 6 days, the lead-exposed rats appear to have adjusted their meal siz e and meal duration to approximately control values. However, this com pensation appears to have occurred at the expense of the daily (noctur nal) number of meals, which decreased slightly (although not significa ntly) in lead-exposed animals. Thus, the total daily intake of food in lead-treated animals remained depressed relative to control animals.