Evidence for a differential distribution of reducing equivalents from NADPH in cartilage.

It has been suggested that the NADPH, generated from the activity of glucose 6-phosphate dehydrogenase, may be utilized by two different routes, namely either for biosynthesis purposes (type 2) or for microsomal respiration (type 1). This concept has been tested in the rabbit ear model in which an injection of papain into the rabbit causes loss of proteoglycans of the auricular matrix followed by its restoration over the following eight days. It is shown that whereas the type 1 pathway was either unaltered or diminished, the doubling of the glucose 6-phosphate dehydrogenase activity was related solely to the type 2 pathway.