Vitreal elimination kinetics of large molecular weight FITC-labeled dextrans in albino rabbits using a novel microsampling technique
✍ Scribed by Clapton S. Dias; Ashim K. Mitra
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 189 KB
- Volume
- 89
- Category
- Article
- ISSN
- 0022-3549
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✦ Synopsis
A novel sampling technique that allowed for continuous vitreal sampling of high molecular weight compounds was developed. This technique generated consistent and reproducible results. Fluorescein isothiocyanate-linked dextrans (FITC-dextrans) with average molecular weights of 4.4 , 9.3, and 38.9 kD were selected for the study. A 100 g dose was administered into the vitreous by a short-term infusion (100 L) over a period of 45 s, and sampling was carried out for 10 h. The vitreal elimination of these dextrans was found to follow apparent first-order elimination kinetics, having half-lives of 246 min, 275 min, and 484 min, respectively. Aqueous levels were also determined at the end of 10 h and were correlated with vitreal dextran concentrations. The FITCdextrans displayed an initial equilibration phase of about 200 min followed by linear first-order elimination. Apparent diffusion coefficients in the vitreous have been calculated to be 7.56 × 10 -6 and 6.18 × 10 -6 cm 2 /s for 4.4 and 9.3 kD dextrans, respectively. Furthermore, it became evident that with progressively higher molecular weight FITCdextrans the vitreal elimination rate constant gradually decreased. The elimination rate constant was found to be inversely related to the logarithm of molecular weight with a correlation coefficient of 0.983. Results obtained suggest an elimination mechanism primarily involving the transretinal route possibly with some involvement of the aqueous pathway.