Effect of stimulus on the chemical composition of human tears.

We examined the effect of the nature of the stimulus on the chemical composition of human tears. The protein concentration of emotional tears from women exceeded that of irritant-induced tears by 24% (P less than .01). Polyacrylamide disk gel electrophoresis disclosed no significant difference between the distribution of positively or negatively charged proteins of irritant-induced and emotional tears. Manganese concentrations in tears (30 ng/ml) exceeded serum concentrations from the same subjects by 30-fold. These manganese concentrations in tears were considerably less than previously reported values. We found no differences for the concentrations of protein or manganese in human tears between the sexes.