Histotopochemical determination of metabolic activity of carbohydrate metabolism in plaque from sound and carious enamel.

Abstract

The tetrazolium technique was applied in tissue sections from sound and carious enamel plaque on human teeth to represent the histotopochemical distribution of activity for numerous enzymes of the Embden-Meyerhof pathway, the pentosephosphate and citrate cycle, and the glycerophosphate cycle. GAPDH, LDH, G6PDH, ME, MDH, SDH, and NAD-IDH were found in all samples from sound enamel plaque; NADP-IDH appeared in a few. In plaque from carious enamel, all enzymes tested were found constantly in all samples. There was high enzyme activity in the outer bacterial layer of plaque from sound enamel, whereas the bacterial layer adjacent to the enamel showed substantially less activity. In contrast to the other enzymes, LDH generally showed a relatively low level of activity with signs of stronger activity in the inner layer adjacent to the enamel than in the outer layer. In plaque from carious enamel, the activity of the enzymes tested showed a definite increase from the outer to deeper layers, and was highest in the bacterial layer next to the enamel. The distribution pattern of LDH coincided with that of the other enzymes tested. A semi quantitative differentiation of enzyme activity in the two types of plaque showed that microorganisms in plaque from carious enamel have greater catalytic activity in carbohydrate metabolism than comparable microflora in plaque from sound enamel. From a functional point of view, the total biotope plaque was subdivided into further partial biotopes, characterized by different enzymic activities.