We are endeavoring to increase understanding of transport of inorganic ions and organic nutrients across cellular plasma membranes in the ocular lens. Little is known about transport of anions in this tissue. Kinetic studies will be done with radioactive ligands to clarify the specificity and capacity of transport-systems for halides, bicarbonate, D- and L-lactate, pyruvate, short and medium chain-length aliphatic carboxylates and aromatic carboxylates. These will include analysis of the nature of inhibition and comparison of KT and KI for relevant anions. The effects are to be evaluated of protein group-reagents and other inhibitors of transport to additionally delineate the individuality of transport-systems. The influence of pH on uptake of carboxylates will be determined to assess participation of the dissociated and undissociated forms, and effects on pH of cellular transport of carboxylates will be estimated. These studies are important because exit of lactic acid may eliminate metabolically generated H+ from the lens. Efforts will be made to differentially label the transporter(s) for hexose with (3H)-fluoro-2, 4-dinitrobenzene and for nucleosides with (3H)-N-ethylmaleimide. Affinity labeling will be attempted fo the L- and Ly+ systems for amino acids with 6-diazo-5-oxo-L-norleucine, of the Cl- system with N-(4-azido-2-nitrophenyl)-2-aminoethyl sulfonate, and of the nucleoside transporter(s) with 8-azidoadenosine (a photoaffinity label) and S-(p-nitrobenzyl)-6-thioinosine. Subsequently, plasma membranes are to be isolated, polyacrylamide slab gels run on the solubilized membranes, and the labeled zones identified by scintillation-counting the sliced gel or by fluorography. Transport will be characterized of Ca++, hexose and amino acids in the lens of the Emory mouse, which provides a convenient model of senile cataract in the human. We believe this work will contribute to understanding of cellular transport in lens, which is dependent on diffusion of nutrients from the aqueous humor. The nature of passage of lactate across the plasmalemma is of considerable interest in this primarily glycolytic tissue. As deficiencies in transport can develop in cataractogenesis, this research may have clinical significance. In this connection, critical experiments are to be performed on normal and cataractogenic human lenses.
| Enger, C; Jabs, D A; Dunn, J P et al. (1997) Viral resistance and CMV retinitis: design and methods of a prospective study. CRVR Research Groups. Cytomegalovirus Retinitis Viral Resistance Research Group. Ophthalmic Epidemiol 4:41-8 |
