Pregnancy stimulates secretion of adrenocorticotropin and nitric oxide from peripheral bovine lymphocytes

The cross-talk between the endocrine and the immune systems mediated by a w ide array of hormones, cytokines, and neuromodulators is heightened during disease, stress, and presumably, during pregnancy. Adrenocorticotropin (ACT H) and nitric oxide (NO) are two immunomodulators that are also produced fr om lymphocytes and contribute to the immunomodulation. Thus, we investigate d whether the heightened bidirectional communication between the immune and the endocrine systems observed during pregnancy is reflected in production of ACTH and NO from peripheral bovine lymphocytes and if any temporal corr elation exists between them. Adrenocorticotropin was analyzed using a sandw ich immunoradiometric assay, and nitrite and nitrate (a measure of NO) were estimated in supernatants of cultured peripheral blood lymphocytes (PBLs) using a colorimetric assay based on the Griess reaction. A significantly hi gh secretion of ACTH and NO was noticed from PBLs in all stages of pregnanc y compared to that in cyclic and cystic cows. Increased secretory capacity was noticed as early as 7 days after conception, which reached as much as 6 00% that of nonpregnant animals between Days 90-120 of gestation. Adrenocor ticotropin and NO decline 1 mo before the expected time of parturition. Unl ike those from cyclic animals, PBLs from pregnant cows were refractory to s timulation by PHA-M (Phytohemagglutinin) and corticotropin-releasing hormon e. A strong correlation was observed between ACTH and NO secretion from PBL s in pregnant, in cyclic, and in cystic cows. To our knowledge, this is the first evidence elucidating the induction of ACTH and NO from PBLs during p regnancy, and it implies a new role for ACTH and NO secreted from PBLs in r ecognition and, probably, maintenance of pregnancy.