Cornea fluid dynamics. II. Evidence for transport of radiolabelled albumin in rabbits by bulk flow.

Transport of radiolabelled albumin in vivo has been measured in cornea. In anaesthetized rabbits, a 1-10 nl mixture of either 125I- or 131I-labelled human serum albumin and fluorescinthiocarbamoyldextran was injected with micropipettes under guidance of a fluorescent microscope. The injection sites were a spot 3 mm from limbus and the cornea centre, and the sites were localized by a template fitting the cornea exactly. Four, 12, 20 and 30 hr after the injection, the rabbits were reanaesthetized, and enucleated after being killed with an overdose of anaesthetic. The bulbi were frozen, and dissection of cornea performed in the cold room using the template described above and a stereomicroscope. Numbered samples were obtained, and isotope distribution measured. In the experiments lasting for 20 hr, about 55% of the isotope was recovered, giving a transfer coefficient of 0.4-0.5 per day. A common pattern of isotope distribution was observed independent of duration of isotope equilibration; peripherally injected isotope moved preferentially in central direction, indicating that fluid is transported by bulk flow and diffusion from peripheral to central cornea. Centrally injected isotope moved symmetrically from the injection point, as expected from transport by diffusion alone. Data from experiments with isotope injection in the cornea centre allowed the calculation of a diffusion coefficient for albumin along cornea of 2.19 x 10(-7) cm2 sec-1.