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The Effects of Lactose on the Absorption and Retention of Dietary Lead¹

Department of Biochemistry, College of Agriculture and Life Sciences, University of Wisconsin-Madison, Madison, WI 53706

Intubated lactose has been shown to facilitate the absorption and retention of radiolabeled tracer lead in weanling rats. The conditions under which this effect may be observed are specified here. In acute radiotracer studies with fasted rats, absorption of intubated lead from the intestines and lead uptake into kidney, liver, blood and brain were increased by lactose (3–6 mg/g, per os) in rats 22 and 26 days of age postpartum. However, neither absorption nor uptake and liver were affected in the suckling rat (<21 days postpartum), nor beyond the first week after weaning. The facilitation by lactose of lead absorption and uptake was inhibited by carrier lead concentrations of 100 and 1000 ppm. Lactose at 80 mM (the concentration in rat's milk) had no effect on absorption and uptake of lead, nor on excretion of parenterally administered lead. Chronic feeding of 80 mM lactose and lead (0, 10, or 100 ppm in diet) reduced the retention of lead in kidneys and bones of weanling rats, fed both a normal (0.47%) and a calcium-deficient (0.02%) diet. It is concluded that intubations of high concentrations of lactose into fasted weanling rats can cause an increase in the absorption and uptake of lead. When fed to weanling rats at physiological concentrations, however, lactose actually reduces the retention of lead in bone and kidney.

KEY WORDS: • lactose • intestine • lead • lead absorption

¹ Supported by postdoctoral fellowship ES-05147 to Philip J. Bushnell, Food and Drug Administration contract RFP 223-77-2166, and the Harry Steenbock Research Fund of the Wisconsin Alumni Research Foundation. A part of these data were presented at the annual meeting of the Society of Toxicology, Feb. 24, 1982, Boston, MA (see ref. 28).

² Present address: New York University Medical Center, Institute of Environmental Medicine, 550 First Avenue, New York, New York 10016.

³ No reprints will be available from the authors.

Manuscript received 9 June 1982.