Vitreous fluorophotometry in three models of experimental diabetes mellitus

Fluorophotometry was performed on rats eight to ten days after they were made diabetic with streptozotocin (85 mg/kg), alloxan (50 mg/kg), or pancreatectomy. When compared with normal control animals, no significant differences in aqueous or vitreous fluorescein levels were noted in any of the diabetic models studied. We did note significant depressions of plasma fluorescein levels in pancreatectomized and streptozotocin-treated rats. We normalized our data for these plasma differences by calculating the ratios of aqueous and vitreous fluorescein to plasma fluorescein levels (RA and RV). Both RA and RV were significantly elevated in streptozotocin-induced diabetes; RV alone was elevated following pancreatectomy, while no change in either ratio was apparent in diabetes induced with alloxan. Treatment of streptozotocin-diabetic rats with cortisol for one week caused plasma fluorescein levels and RV to return toward normal, although RA remained elevated. We are cautious in assigning any meaning to changes in RA and RV, especially in view of the paucity of information on the behavior of fluorescein in the blood.