Prolactin and other Lactogenic Hormones

Abstract

In mammals, Prolactin (PRL) is involved in the stimulation of mammary gland growth and lactation; it has a luteotropic and luteolytic effect and also stimulates the growth and secretion of male accessory sex organs. In the laboratory, two myeloid cell lines, a monocyte line, three B cell lines, and three T cell lines, all of human origin, were examined by radioreceptor assay for the presence of lactogenic or growth hormone (GH) receptors, using I-human GH as tracer. PRL is related structurally to GH and placental lactogen. The development and function of the mammary gland is regulated by PRL and steroid hormones. The secretory immune system of the mammary gland could be activated in female or in castrated male mice by combined treatment with progesterone, estrogen, and PRL. Since la antigens are known to have immunoregulatory function, the authors suggested that this hormone induced expression of la antigen may play a fundamental role in the activation of mammary immune system.