A possible linkage of atrial natriuretic peptide to the immune system.

Recent work has suggested the existence of atrial natriuretic peptide (ANP)-like material in lymphoid follicles of the guinea pig intestine. To follow the hypothesis of an association of ANP with the immune system, we now report that the rat thymus, a primary lymphoid organ, is a site of ANP synthesis. This is based on the following experimental evidence: firstly, the material detected corresponds chromatographically with the precursor of ANP. Secondly, the existence of mRNA for ANP in the gland suggests synthesis of the peptide in the gland. Thirdly, immunohistochemical studies locate ANP-like material in cortical thymocytes, predominantly in the subcapsular areas of the thymus. Both ANP-like material and mRNA were present to a larger extent in very young rats. The results communicated here support the notion of a link of ANP with the immune system.