Methanol poisoning: ocular toxicity produced by formate.

formate accumulation in blood, Formaldehyde was not measurable in an y fluids or tissu e. Experiments were designed to study the possible role of formate in ocular toxicity. Formate was administered by iv infusion in the form of formate b uffer for the purpose of maintaining pH in the normal range. The rate of formate infusion was adi ted to maintain blood formate at toxic concentration. No formaldehyde was detected. Resultswere similar to those described for methanol poisoning: optic disc edema with a normal vascular bed and intracellular edema with intraaxonal swelling. t Cif 1 V M¢hl < 1)' y ^ h City ^^' W t ^ o h ^ ! t, Y m t l)C 3 1`c1 Y l 1 ' ' J Methanol poisoning in man and in monke y s is characterized by severe metabolic acidosis and marked ocular toxicity Recently, several laborato ries have reported the accumulation of formic acid in the blood of monkeys which had become severely acidotic after the administration of methanol (McMartin et aL, I975; Clay el W J^-11 ^, 1+ a!.,1975; Martin-Amat et al., 1977a). In fact, those authors have reported on decreases in blood bicarbonate concentration s which uate with elevated blood formate v ues. It m `t r i 1^ would appear that formic acid accumulation responsible for metabolic acidosis produced in methanol poisoning in the monkey. a The ocular toxicity produced aft er methanol administration in monkeys has recently t' I ° w A C, been explored. Monke y s maintained on an experimental regimen with blood formate values of about 10 m /liter and arte rial blood pH values of 7.1 to 7.3 (Martin-Ama1_el a!., 1977a)) consistently had serious optic disc edema and loss of the pupifary response to light H ayreh et al., 1977). The optic disc edema appears similar to the ocular xtcity described in humans (Benton and Calhoun, 1954). Histopathologic evaluation of the optic nerves (Baumbach et al., 1977) s howed intraaxonal swelling in the anterior en-segn t F ' j e optic nerve with otherwise normal retinae, including normal ganglion cells, Since elevated formate concen tr ations occurred in the presence of metabolic acidosis in animals displaying ocular toxicity, we tested the possibility that formate alon e was