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Biliary Manganese Excretion in Conscious Rats Is Affected by Acute and Chronic Manganese Intake but Not by Dietary Fat^1,2,3,

Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706 ^* Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108

We hypothesized that biliary excretion of manganese would be sensitive to acute and chronic variations in manganese and fat intakes. In the acute study, we gavaged rats with solutions containing ⁵⁴Mn with either 0, 0.2, 1 or 10 mg Mn as MnCl₂. We collected bile from unanesthesized rats that were simultaneously reinfused with bile acids. Total manganese excretion (from 0.5 to 6.5 h after dosing) was proportional to the acute doses (approximately 3.4% of doses). In the chronic study, weanling rats were fed diets containing 5 or 20 g corn oil/g diet and 0.49 or 72 µg Mn/g diet for 8 wk and then deprived of food for 12 h before bile collection. Manganese-deficient animals excreted only 0.7% as much manganese in bile as manganese-replete animals, but this reduction was not sufficient to prevent 50–80% reduction of tissue manganese concentrations. Moreover, biliary manganese excretion (calculated for 24 h) by both manganese-deficient and manganese-replete rats (deprived of food for previous 12 h) accounted for only 1% of their manganese intake on the previous day. Dietary fat and manganese concentrations had few effects on excretion of total or individual bile acids. Ours is the first report of biliary excretion of orally administered manganese by conscious rats.

KEY WORDS: • manganese • bile • bile acids • dietary fat • rats

¹ A portion of this work was presented at Experimental Biology 94, April 24–28, 1994, Anaheim, CA [Malecki, E. A., MacNeil, G. & Greger, J. L. (1994) Fasting and postprandial biliary manganese (Mn) secretion in conscious rats fed varying levels of diet Mn and fat. FASEB J. 8: A429 (abs.)].

² Supported by the College of Agricultural and Life Sciences (University of Wisconsin-Madison) project no. 2623, NIH grant R01-DK41940, and a National Science Foundation Graduate Fellowship (to EAM).

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence should be addressed.

Manuscript received 26 May 1995. Revision accepted 10 October 1995.