Prolactin is a neuroendocrine hormone secreted by the pituitary gland. Its primary function is to promote and maintain lactation during pregnancy and suckling. In addition, prolactin plays an immunoegulatory role by stimulating the activities of ornithine decarboxylase and protein kinase C, which are important for the proliferation, differentiation, and function of lymphocytes. Recombinant Rat Prolactin is a 22.6 kDa globular protein containing 198 amino acid residues.