Insulin concentrations in aqueous humor after paracentesis and feeding of rabbits

Although the lens has been shown to have the capacity to respond to insulin in vitro, little is known concerning the biochemical relationships of insulin to the lens in vivo. Therefore we have measured insulin in the aqueous humor of rabbits by a sensitive radioimmunoassay after paracentesis and feeding. The insulin concentration in aqueous humor was 3% of that in plasma. One hour after paracentesis the aqueous humor insulin concentration was increased sixfold, apparently due to breakdown of the blood-aqueous barrier, but 1 week after paracentesis it had returned to its original level, apparently because of restoration of the blood-aqueous barrier within that time. After feeding, the aqueous humor insulin concentration was increased by 30% compared to a 175% increase in plasma. Factors influencing the aqueous humor insulin concentration and the possibility of insulin influence on lens metabolism are discussed.