Urocortin-like immunoreactivity in the primary lymphoid organsof the duck (Anas platyrhynchos)

摘要

Urocortin (UCN) is a 40 aminoacid peptide which belongs tocorticotropin-releasing factor (CRF) family. This family of pep-tides stimulates the secretion of proopiomelanocortin(POMC)-derived peptides, adrenocorticotropic hormone(ACTH), β-endorphin and melanocyte-stimulating hormone(MSH) in the pituitary gland. In the present study, usingWestern blotting and immunohistochemistry, the distributionof UCN in the primary lymphoid organs of the duck was inves-tigated at different ages. In the cloacal burse and thymus,Western blot demonstrated the presence of a peptide havinga molecular weight compatible with that of the mammalianUCN. In the cloacal burse, immunoreactivity was located in themedullary epithelial cells and in the follicular associated andcortico-medullary epithelium. In the thymus, immunoreactivitywas located in single epithelial cells. Double labellingimmunofluorescence studies showed that UCN immunoreac-tivity completely colocalised with cytokeratin immunoreactivityin both the thymus and cloacal burse. Statistically significantdifferences in the percentage of UCN immunoreactivity wereobserved between different age periods in the cloacal burse.The results suggest that, in birds, urocortin has an importantrole in regulating the function of the immune system.