Segmental Heterogeneity and Regulation of Electrolyte Transport in the Rabbit Large Intestine

Abstract

Ion transport across rabbit colon has been a subject of investigation for more than 20 years. Based on fundamental principles of ion transport found in frog skin (Ussing and Zerahn 1951), the pioneering studies of Schultz and associates (Frizzell et al. 1976; Schultz et al. 1977; Turnheim et al. 1977, 1978, 1987; Frizzell and Schultz 1978; Frizzell and Turnheim 1978) elaborated the first detailed cellular models of sodium, potassium and chloride transport in rabbit colon. At that time, only the descending colon was investigated, and investigators aimed to find general models for ion transport in the mammalian colon (Schultz 1981, 1984). After some more years of research on this and other mammalian colonic epithelia, remarkable species differences in colonic ion transport became evident, and in many species under investigation, a pronounced segmental heterogeneity of transport functions was found (Clauss et al. 1985a; Halm and Frizzell 1991). Ion transport mechanisms along the large intestine differ not only gradually and quantitatively, but qualitatively, and are organized in a way to enable the particular specificity of digestive functions in various animals. The rabbit large intestine is a special example of such a complex diversity, contributing to a unique digestive mechanism.