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Cyclic AMP Metabolism and Nucleic Acid Content in the Lymphocytes of the Thymus, Spleen, and Lymph Nodes of Protein-deficient Rats¹

Laboratorie d'Hématologie Nutritionnelle, Centre Marcel Delépine, Centre National de la Recherche Scientifique, 45045 Orléans Cédex, France

The concentration of cyclic AMP (cAMP) and its metabolites (5'-AMP and adenosine) as well as the adenyl cyclase, cAMP phosphodiesterase, and 5'-nucleotidase activities were determined in lymphocytes of thymus, spleen, and lymph nodes of control and protein-deficient rats. The values of these parameters, when expressed as per milligram DNA and as per 10⁸ cells, but not always when expressed as per milligram protein, were much lower in the thymus as compared with the spleen and the lymph nodes in the control rats. The protein-deficient diet increased the nucleotide concentrations in the thymus and spleen lymphocytes on a per milligram DNA basis except those of thymic cAMP, which did not change. The same diet also increased the activities of the enzymes involved in the cAMP metabolism in thymic, splenic, and lymph node lymphocytes. Such a peculiarity could be related to the reduction of the mitotic activity of lymphocytes caused by protein deficiency since an inverse relationship has been reported between this activity and the synthesis of cAMP. On the other hand, it was noted that purified lymphocyte suspensions contained paradoxically higher amounts per cell of DNA, RNA, and protein in the thymus, spleen, and lymph nodes of protein-deficient rats as compared with those of the control rats. However, when the cell preparations were not purified, only the lymph node cells displayed a strong increase in their DNA content. Prolongation of the S phase of the cell cycle in these lymphocytes is suggested.

KEY WORDS: • cyclic AMP • DNA • RNA • lymphocytes • protein deficiency

¹ Part of this paper was presented at the French Society of Biology (July, 15, 1974, in Paris, France) and at the 26th International Congress of Physiological Sciences (October 25, 1974, in New Delhi, India).

² U. Srivastava was a recipient of a France-Quebec and a France-Canada exchange grants. Present address: Institute de Diététique et de Nutrition, C.P. 6128, Université de Montréal, Montréal, P.Q. Canada.

Manuscript received 13 October 1974.