Oxygen uptake by canine uveal tissue: in vitro and in vivo methods compared.

This study was done to determine whether newer in vitro methods for measurement of uveal tissue respiration would corroborate QOt values previously obtained using such in vivo methods as isolated organ perfusion or sampling of ocular arteries and veins in the anesthetized dog. A good correlation exists among QOt values found with each of these three methods involving both iridociliary and choroidal tissue samples. Normal QOt values (one liter per dry milligrams per hour) ranged between 0.71 and 0.82 for both the in vitro Warburg-type measurement, using an oxygen electrode, and the in vivo sampling of the cannulated ocular vessels. Isolated organ perfusion with whole blood gives a somewhat higher value (1.90) when retinal uptake is obviously included. When retinal extraction of oxygen is suppressed, normal values representing uveal uptake are found. Serum uveitis reduces uveal extraction of oxygen in all three systems: hyperthermia increases it (Fig. 1).