A systematic approach to the analysis of intestinal transport kinetics.

A statistical technique for the estimation and differentiation of the operational kinetic parameters for influx of solutes into intestinal rings incubated in vitro is presented. Influx data were fitted to an equation comprising the sum of saturable and diffusional components; the latter is assumed to include entry into the extracellular space, thus avoiding the necessity of indirect assessment with space markers. The estimations are made by non-linear regression analysis on a logarithmic scale. Comparison between data sets is carried out by performing a joint fit under the restriction of parameters common to the two sets. If an F-test reveals no significant loss of information, then the parameter(s) in question do not differ from one set to another. The method is illustrated by an experiment to determine which kinetic parameters for influx of beta-methyl-D-glucoside are altered when sodium is removed from the incubation medium. The results show that the Km is principally affected by this manoeuvre.