A study of the C14-glucose metabolism of the rabbit lens.

Because of its low oxygen consumption, about 0.1 &/mg./hr., the ocular lens has been considered as a metabolically inert tissue. However, any interference in the carbohydrate metabolism results in the opacification of this normally transparent organ. Therefore, it appears that metabolism is essential for the viability of the lens. That a consumption of oxygen, even if low, is also necessary was evidenced by Harris et al. (1) who found that the lens is incapable of maintaining its intracellular ionic composition without the presence of oxygen. Many attempts have been made to determine the pattern of glucose metabolism in the ocular lens. Studies with lens homogenates have shown the presence of enzymes of the EmbdenMeyerhof pathway (2, 3), the citric acid cycle (4), and the phosphogluconate oxidation pathway (5, 6). Differences observed in the oxidation of glucose-l-Cl4 and glucose-6-Cl4 have suggested the participation of the phosphogluconate oxidation pathway in the production of CO2 (5). To obtain this information by the conventional techniques in vitro, considerable quantities of material had to be used, since the lens is a relatively inactive tissue. The development of the lens culture technique (7,8) has made it possible to incubate the lens for a longer period of time and to allow a study of the metabolism of a single lens. The lens is particularly well suited for the organ culture procedure, since its habitat in situ can be more easily duplicated than that of other organs which are dependent on a direct supply of blood. Being avascular, the lens must receive nutrients from the bathing medium and dispose of end products of metabolism into it. This report deals with a study of the glucose metabolism of an intact organ in a system in vitro by the use of the culture technique. An attempt is made to evaluate the pattern of C14glucose metabolism of the rabbit lens which is maintained for 24 hours in an environment closely simulating the physiological conditions which exist in the eye.