American Journal of Clinical Nutrition, Vol 13, 378-384, Copyright © 1963 by The American Society for Clinical Nutrition, Inc.

Inhibition of d-Pantothenate by l-Pantothenate in the Rat

¹ From the Department of Nutritional Research, Mead Johnson Research Center, Evansville, Indiana

The biologic effects of the unnatural l(—) isomer of calcium pantothenate were studied in male weanling rats. With both low and adequate levels of d-pantothenate in the diet, addition of the l isomer in an amount equal to that of the d-pantothenate had no apparent effects on weight gain, as was found with racemic pantothenate in earlier studies. However, addition of a relatively large excess of l-pantothenate inhibited growth and, in rats receiving no d-pantothenate, aggravated signs of deficiency and led to more rapid death. The levels of l-pantothenate found necessary to depress growth with both low and adequate levels of d-pantothenate in the diet indicated that the inhibition was competitive. When l-pantothenate was present in the diet at ten times the level of d-pantothenate, no marked decreases in weight gain were detected, but with a twentyfold to thirtyfold excess or more, significant inhibition occurred.

Acetylating ability of the rats after four to eight weeks on the test diets was markedly decreased in animals on the pantothenic-deficient diet or on diets containing levels of l-pantothenate which depressed growth. Feeding excess l-pantothenate led to enlargement of the adrenal glands and histologic changes which were similar to those found in pantothenate deficiency.

Liver d-pantothenate was decreased in rats receiving excess of the l isomer. From measurements of total -alanine in the liver it appears that there may be accumulation of small amounts of l-pantothenate in the liver.