Development of intestinal transport function in mammals

Considerable progress has been made over the last decade in the understandi ng of mechanisms responsible for the ontogenetic changes of mammalian intes tine. This review presents the current knowledge about the development of i ntestinal transport function in the context of intestinal mucosa ontogeny. The review predominantly focuses on signals that trigger and/or modulate th e developmental changes of intestinal transport. After an overview of the p roliferation and differentiation of intestinal mucosa, data about the bidir ectional traffic (absorption and secretion) across the developing intestina l epithelium are presented. The largest part of the review is devoted to th e description of developmental patterns concerning the absorption of nutrie nts, ions, water, vitamins, trace elements, and milk-borne biologically act ive substances. Furthermore, the review examines the development of intesti nal secretion that has a variety of functions including maintenance of the fluidity of the intestinal content, lubrication of mucosal surface, and muc osal protection. The age-dependent shifts of absorption and secretion are t he subject of integrated regulatory mechanisms, and hence, the input of hor monal, nervous, immune, and dietary signals is reviewed. Finally, the utili zation of energy for transport processes in the developing intestine is hig hlighted, and the interactions between various sources of energy are discus sed. The review ends with suggestions concerning possible directions of fut ure research.