Lens organ culture. I. Methodology and metabolic evaluation

Effect of ketoacids on H(2)O(2) induced cataract

Cataract is one of the leading causes of visual disability often leading to blindness in the elderly population. One of the causes is oxidation of proteins present in lens, by hydrogen peroxide (H(2)O(2)). In the present study 100 goat lenses were analyzed to determine the protective efficacy of ketoacids, against the oxidative insult by H(2)O(2). The ketoacids used were (pyruvate, alpha ketoglutarate and oxaloacetate), that are constantly produced endogenously. The lenses were incubated as control and experimental groups in TC-199 media for 72 hrs. H(2)O(2) concentration of 10mM was used to induce cataract. The biochemical parameters measured were levels of malondialdehyde (MDA), a lipid peroxidation product and activity of glutathione peroxidase (G-Px), an enzymatic antioxidant. The results showed a significant increase in the levels of MDA and significant decrease in the activity of G-Px in the cataractous lenses as compared to control. After addition of ketoacids (pyruvate (10mM), alpha ketoglutarate (20mM) and oxaloacetate (20mM)) separately, the levels of MDA decreased significantly and the activity of G-Px increased significantly. The results suggest that the ketoacids can be very promising antioxidants for the treatment of cataract. They may also be useful in treating other disabilities related to acute and chronic oxidative stress.

Ascorbic acid uptake by young and aged guinea pig lenses

The dynamics of in vitro uptake of [14C]-ascorbic acid into intact lenses of young (50 days old) and old (730 days old) guinea pigs was evaluated in this study. Two-dimensional protein gel analysis of [35S]-methionine labeled proteins provided evidence that the isolated lenses were viable throughout the culture period. It was found that the in vitro uptake of ascorbate into these lenses follows similar saturation kinetics for lenses from both age groups. Moreover, the linear uptake rate was identical. Ascorbate transport was inhibited by phloretin, p-chloromercuribenzoate, insulin, glucose and ouabain; however, no inhibition was observed with 2,4-dinitrophenol or NaF. These results suggest that the lenticular ascorbate concentration is regulated by a facilitated diffusion process and it not energy-dependent. Data on ascorbate transport into lenses from aged guinea pigs provide strong evidence that the abnormally low ascorbic acid concentrations in lenses of old mammals is not likely the result of a decreased lenticular uptake ability.

Growth and transparency in the lens, an epithelial tissue, stimulated by pulses of PDGF

The rat lens undergoes dramatic growth during early postnatal development. Lens weight increased by a factor of 23 in 26 days. Growth rate per day oscillated between 0 and 87 percent. A new culture system was designed to study the oscillations in growth during development. Lens growth and transparency in vitro required pulsatile delivery of platelet-derived growth factor (PDGF) in HL-1 serum-free medium. Continuous delivery of HL-1 medium with PDGF or pulsatile delivery of HL-1 medium without PDGF resulted in lens opacity and no growth. These results provide direct evidence that PDGF stimulates an epithelial tissue and that oscillations in growth occur during normal development of the rat lens.

Progressive microscopical changes in the closed system incubated rat lens

A phase contrast microscopy investigation of 18 cultured rat lenses was undertaken. After an initial latent phase, the outline of the epithelial cells anteriorly became enhanced and posteriorly the lens fibers began to swell. This was followed by an anterior and posterior subcapsular accumulation of fluid, epithelial swelling and formation of posterior subcapsular vacuoles. At the end of the incubation period, no increase in the light dissemination from the lens was observed. It is concluded, that, when these changes are taken into account, the closed system cultured rat lens is an excellent and applicable model for studying the induced progressive changes in the microstructure of the living lens due to different agents.