Effect of renal formic acid excretion on urinary calcium and ammonia concentrations.

Intragastrically given formic acid (300 mg/kg) caused high urinary formate concentrations in rabbits with continuously decreasing urinary pH up to 30 h after the dose despite the fact that the bulk of the formate in urine was excreted within 15 h. Urinary formic acid inversely correlated to urinary ammonia in 23 workers occupationally exposed to methanol or formic acid so that the delayed urinary acidification could have been caused by the effects of formate on renal ammonia genesis. The urinary excretion of calcium was linearly correlated to the formic acid excretion by the same subjects. The latter effect may have been caused by interferences with the tubular reabsorption mechanisms for the calcium ion.