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A method is introduced which enables the two-dimensional detection and analysis of absorbancy-values from continuous dye-deposites with rather low data storage capacity. Applied to histochemical reactions this method is used for kinetic analysis of enzymes along the intestinal villus. Its main part consists of two programs for two dimensional scanning, i.e. along the villus and at right angle from the lumen across the brush-border membrane to the apical cytoplasma. Two further programs serve as prerequisites: the automatical detection of mean values and the description of absorbancy spectra in the tissue section. The measurements are carried out with a MPVII Leitz in connection with a Hewlett Packard 9815 A calculator. The study of alpha-glucosidases of the human small intestine is taken to demonstrate the value of the method. It is shown that a similar Vmax-gradient along the villus can be demonstrated as by microchemical methods. Thus this method enables the description of the kinetic properties of a distinct enzymatic activity in preserved tissue sections on the cellular level and the possible alterations of Vmax and Km in context to the morphological pattern.

In order to test the influence of thyroid hormones on small intestine function, adult female Wistar rats were injected daily with either 100 microgram/100 g body weight tetraiodothyronine or placebo. After 12 days, jejunal segments were removed and processed for morphometric analysis of mucosal architecture and quantitative histochemical determinations of the apparent Km- and Vmax-values of lactase/beta-glucosidase and neutral alpha-glucosidase at constant basal and apical measuring positions along the villi. The villus-crypt-architecture was the same in both experimental groups. At the cellular level, however, application of tetraiodothyronine resulted in a marked decrease in the apparent Vmax of lactase/beta-glucosidase at both villus positions, maintaining the normal activity gradient along the villi. In comparison with the controls, a less pronounced but significant reduction in activity was also demonstrated for the neutral alpha-glucosidase. Substrate affinity, however, was only increased for this enzyme, the apparent Km of lactase/beta-glucosidase not being affected by the hormone. The results indicate a direct effect of tetraiodothyronine on jejunal brush border disaccharidases of the rat. The alternative mechanism, an effect mediated by an altered enterocyte turnover is unlikely to occur.