Prolactin and the physiological regulation of its secretion. A review

This review briefly summarizes recent findings on lactotrophs in the pituitary gland and extrapituitary tissues as a no homologous group cell types of different embryonic origin, morphology and biological function. They display a remarkable adaptation to altered physiological condition. Their functions are derived from structural polymorphism, local synthesis, divergent intracellular signaling pathways and target genes. Most of them are heterogenous with respect to basal hormone release, electrical activity and responsiveness to stimulatory/inhibitory factors, depending upon gender and physiological state of animal. The circulating prolactin (PRL) produced by many types of lactotrophs can act in edocrine/paracrine/autocrine manner, respectively as a hormone, growth factor, neurotransmitter or immunoregulator. At the cellular level PRL exerts mitogenic, morphogenic and secretory activity. Numerous factors of the central and peripheral origin are involved in the mechanism regulating PRL secretion, causing an increase or decrease of the hormone concentration in the circulation. The certain feedback mechanism keep the pituitary lactotrophs to be not overactive.