Amino acid supplementation: its effect on the thymus in growing rats.

Previous papers have indicated an arrest in cellular proliferation and maturation of the thymus of rats fed at weaning a 6.5% protein corn diet. In this report, we studied the status of the thymus of growing rats fed from weaning and during 10 days a 6.5% corn diet supplemented with all the essential amino acids to resemble the amino acid pattern of a high quality protein (casein) (group Ms), or only with the first limiting amino acid, lysine (group Ml). The control group received a 6.5% casein diet (group C). At the end of the feeding period, animals were killed and thymus tissues were removed. Cell number (Nc) and the mature T cell population characterized by the monoclonal antibody W3/13 using the indirect immunofluores-cence technique were determined. No differences among experimental groups in Nc (Ms:21.0 ± 2.8, Ml:23.2 ± 3.5, C:20.3 ± 6.6), and in the absolute number of W3/13 + T cells (Ms:15.4 ± 2.6, Ml:15.0 ± 2.3, C:13.0 ± 1.3) were observed. These results indicate the important role of l...