pH of organ‐culture‐stored corneas

Abstract

Changes in intracorneal and storage-medium pH values of organ-culture-stored cat corneas were monitored over a 4-week period. The intracorneal pH was determined using the phosphorus-31 magnetic resonance spectroscopy (31P MRS) chemical shift of inorganic orthophosphate in conjunction with a standard pH titration curve. We incubated 32 adult cat corneas using two similar standard organ-culture methods, one with chondroitin sulfate (method 1) and the other without (method 2). Time-course data at 0, 1, 3 and 4 weeks of storage were used to calculate the rate of pH change. The intracorneal pH was not changed significantly for either organ-culture method; however, the storage-medium pH rate of change declined significantly for both methods (method 1, 0.15 pH units/week; method 2, 0.12 pH units/week). The difference between intracorneal and storage-medium pH values over time increased at a rate of 0.12 and 0.11 pH units/week for method 1 and method 2, respectively. The declining storage-medium pH in conjunction with the maintenance of intracorneal pH contributes to an increased metabolic demand on the cornea.

Some metabolic changes during human corneal organ culture

“…The high initial metabolic rate could alternatively be explained by energy demanding synthesis succeeding glucose deprivation during the post-mortem period (Muller et al 1988). The fall in pH is another likely explaining factor for the decreased metabolic activity, although the intracorneal pH has been found to be within normal ranges even if the pH of the medium decreases to 6.9 (Lass et al 1988). Furthermore, a decrease in metabolic activity of human corneal organ cultures has occurred irrespective of a normal medium pH (Lindstrom et al 1976).…”

“…Several studies of metabolism in corneal organ cultures have been performed using different fresh animal corneas at different temperatures: pig, 4"C, 22"C, 31°C (Miiller et al 1988; or cat, 31°C (Lass et al 1988) corneas. However, metabolic studies of human cadaver corneal organ cultures used for keratoplasty are more sparse (Lindstrom et al 1976).…”