| Popis: |
The mechanisms responsible for ion, nonelectrolyte and water transport by the small intestine have been the subjects of extensive investigations for several decades. This chapter will not exhaustively review the numerous transport functions of the small intestine, many of which are as yet poorly understood; rather than this, its purpose is to summarize briefly our current understanding of several central topics that have been the focus of considerable attention in recent years. Specifically, this chapter will be concerned with (a) the characteristics and physiologic consequences of low-resistance paracellular (“shunt”) pathways that traverse the small intestine; (b) current views regarding the mechanisms responsible for transcellular Na transport; and, (c) recent developments dealing with the interactions between Na transport and the transport of other solutes. The emphasis will be on data derived from studies on in-vitro preparations of small intestine, particularly rabbit ileum (for a recent discussion of transport by small intestine in situ the reader is referred to SCHULTZ et al. [1974]). The aim is to bring unresolved problems into sharper focus and to suggest important areas for future research. It is, therefore, inevitable that discussions of controversial issues will be colored by the author’s personal views; he hopes the readers will indulge him this license. |
