Effect of amino acid input rates on lens metabolism in a perfusion culture system

A perfusion system has been established for the organ culture of the lens. The system is designed so that a constant flow of fluid occurs past the lens and a separate channel of fluid simultaneously bypasses the lens. Lens metabolic activity can be determined by analyzing differences between these two samples of fluid. The system also maintains a level of pressure comparable to intraocular pressure. Apparatus for observation and photography of the lens is built into the system. The purpose of these studies was to determine if this perfusion system could maintain the rabbit lens close to the physiological state, to study the metabolic behavior of the lens under steady state conditions, and to determine the effect of increasing amino acid concentrations on the metabolic activity of the lens under steady state conditions. By increasing the amino acid concentrations in the medium we hoped to compensate for the lack of protein in the medium and to provide metabolic substrate to maintain the lens under perfusion conditions. The rabbit lens was cultured at a temperature of 33 degrees C for periods up to 100 h. A totally synthetic perfusion medium without proteins or antibiotics was devised. This medium imitates posterior chamber aqueous humour, except that it does not contain ascorbic acid because it was found that ascorbic acid readily auto-oxidizes and depletes the oxygen content of the medium. The amino acid concentration of the perfusion medium was adjusted so that its total nitrogen content was equivalent to the total nitrogen content of posterior chamber aqueous humour. To determine the metabolic behavior of the lens, 10 different metabolic substances were analyzed in the medium and 15 were analyzed in the lens. These substances are mainly metabolic substrates and end products. As a reference for the evaluation of the behavior of the lens in the perfusion system, the perfused lens was compared to the lens in the other eye of the rabbit. Standards for differences between the right and left lens and the first or second lens removed from the rabbit were developed in control studies. A series of experiments was devised to determine the effect of increased amino acid concentration in the medium on the metabolic behavior of the lens. Concentrations of amino acids from 0 to 7.26 times the posterior concentration of amino acids in chamber aqueous humour were studied. Seven studies were done with a flow rate of medium of about 2 g per h, with each experiment lasting from 80 to 100 h.(ABSTRACT TRUNCATED AT 400 WORDS)