The presence of glycogen in lenses of different species

Abstract

The presence of glycogen in lenses has occasionally been the subject of studies, mostly by histochemical procedures. Quantitative values for the glycogen content are, however, rare. Results obtained by both methods corresponded in so far as the glycogen content of lenses proved to be very low and it is doubtful whether it may be considered at all as a reserve carbohydrate for lens metabolism. After histochemical investigations with acridine-free parosaniline-(PAS)-staining and fluorescence identification with salicylic acid-hydrazide had confirmed the presence of glycogen in the lenses of pigeon, guinea pig, rat, rabbit, calf and bovine, we tried to get more information about such compounds participating in the glycogen cycle. Besides determination of their concentration in total lenses, lens cortex and lens nucleus, the data for their specific activities after incorporation of labelled inorganic phosphate into the organophosphorous-compounds give an indication of the metabolic rates of these reactions. All present findings show that the glycogen present in the lens is located in the nucleus to a considerable degree, which was most obvious in the case of the pigeon lens, being in good agreement with the numerous results Rabaey (1963) obtained with bird lenses. In Rabaey's opinion the importance of glycogen in the nucleus of the bird lens, regarding its special accommodation mechanism, lies in the increase of the refractive index, substituting for the protein of low molecular weight lacking in this region. We however tend to assume that in calf and bovine lenses there is an active participation of glycogen in the carbohydrate metabolism. This may be true also for the lenses of rabbit and rat as well as those of humans.