Effect of Short Fasts on Heavy Metal Absorption in the Rat

Abstract

Recently there have been brief reports that in man and mice fasting for 16 or 24 h increased the retention of a dose of lead given subsequently (Garber and Wei 1974; Rabinowitz et al. 1975, 1980); chronic underfeeding of rats was also found to increase lead retention (Quarterman et al. 1976). No systematic observations have been made about the effects of fasting on the retention of lead or any other heavy metals and in fact most studies of such effects on organic or other inorganic substances have involved total starvation for periods of about three days (Lichtenberger et al. 1976; Newry et al. 1970; Beck and Dinda 1973; Steiner and Gray 1969). Starvation produces both morphological and physiological changes in the intestinal mucosa which include both a reduction in the weight and thickness of the mucosa and in its total DNA content. With fasting periods of 24 h or less these effects, like those on the transport of sugars, fats and some drugs are smaller but still measurable (McManus and Isselbacher 1970; Mead et al. 1951; Orr and Benet 1975). Increases in lead retention caused by short fasts could be important in exacerbating lead intoxication of man and animals and, if fasting affected simiarly the retention of other metals, it could also influence the fate of a range of toxic or essential trace elements after their ingestion.