QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Dryden, L. P. Articles by Hartman, A. M. Search for Related Content PubMed PubMed Citation Articles by Dryden, L. P. Articles by Hartman, A. M.

Vitamin B₁₂ Deficiency in the Rat Fed High Protein Rations¹

United States Department of Agriculture, Agricultural Research Service, Animal Science Research Division, Beltsville, Maryland 20705

Experiments were conducted in an effort to ascertain the reason for the decreased growth response obtained in weanling rats fed vitamin B₁₂-deficient rations as the protein level was raised from 25% to 65% with vitamin B₁₂-deficient casein. The intensified growth depression with the higher protein levels appeared related to the catabolism of the excess protein but did not seem to involve impaired protein digestion or difficulty in handling the end products of nitrogen metabolism. Rather, the vitamin appeared to be concerned in the metabolic disposal of the carbon skeletons of some or all of the amino acids comprising the added protein. As a result of tests in which the individual amino acids were added singly to the 25% vitamin B₁₂-deficient ration in amounts equivalent to those in the 40% added casein, the amino acids involved were identified as valine, isoleucine, threonine and serine. proline tended to have a counteracting effect. The amino acids related to methylmalonate metabolism — valine, isoleucine, and, to a large extent, threonine — apparently contributed to the growth depression on the high protein ration to a much greater extent, relatively, than the one related to formate metabolism — serine.

Manuscript received 28 September 1970.