Study of fluorescein glucuronide

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Abstract
Comparative studies of fluorescein and fluorescein glucuronide were carried out. Binding to human serum protein was studied using an Amicon MPS-3 ultrafiltration unit; it averaged 63% for fluorescein glucuronide and 85% for fluorescein. Intracameral penetration of both compounds was studied in the human eye, and the concentration changes of both compounds in the plasma ultrafiltrate and in the anterior chamber were analyzed, based on Davson's equation. The coefficient of entry into the anterior chamber (k i ) was 0.018 ± 0.007 h−1 (mean ± SD,n = 10) for fluorescein glucuronide and 0.054 ± 0.033 h−1 for fluorescein, and the former was significantly lower than the latter (P < 0.005). The rate of loss from the vitreous (k v ) was studied by injecting each compund into the vitreous of the pigmented rabbit and following the fluorescein intensity changes in it. It was 0.042 ± 0.008 h−1 (mean ± SD,n = 8) for fluorescein glucuronide and 0.17 ± 0.01 h−1 for fluorescein, and the former was significantly smaller than the latter (P < 0.001). Intraperitoneal injection of probenecid significantly decreased thek v of fluorescein but had little effection that of fluorescein glucuronide. It was suggested that fluorescein glucuronide is lost from the vitreous mainly by a passive mechanism.