Transport of organic molecules in the lens

Abstract

The ocular lens is capable of transporting amino acids, peptides and other organic molecules by carrier-mediated processes which are energy and temperature dependent. The energy for this active transport is derived chiefly from the anerobic metabolism of glucose. While the site of active transport is apparently located in the epithelial layer the question whether lens fiber membranes also have active transport mechanisms remains an unresolved problem. Although several amino acids exhibit overlapping affinities for various sites of transport, groups of compounds having structural similarities and certain stereochemical configurations show preference for a specific site of transport. The fundamental question of whether carrier-mediated system(s) for organic molecules in the lens is related directly to sodium-potassium activated ATPase also cannot be answered since the effect of ouabain on the transport of various nonelectrolytes is not always immediate as in the case of sodium and potassium ions. Similarly, further studies are needed to clarify the nature of the coupling mechanism between the transport of cations and organic molecules.