Relationship between Plasma and Tear Fluoride Levels in Rabbit and Man

Abstract

Tear fluoride concentrations were determined in rabbits and man. Tear fluoride levels in reflex tears were higher in rabbits (2–10 µmol/l) than in man (1.4–4 µmol/l), while plasma levels were quite similar in both species (1.5–4 µmol/l). Chronic fluoride ingestion in rabbits over 29 days of 1, 5, 10, 25 or 50 (2.65 mmol/l) ppm fluoride in drinking water caused a dose-related increase in plasma, but not tear, levels of fluoride. The plasma:tear ratio went from 0.5 at baseline (1 ppm) to 1.8 after drinking water that contained 50 ppm F. Acute fluoride ingestion in man led to an increase in both plasma and tear fluoride levels that changed such that the plasmartear ratio remained constant despite a 2-fold increase in plasma fluoride.

Lachrymal Determinations: Methods and Updates on Biopharmaceutical and Clinical Applications

“…Therefore, some authors emphasise the hypothetical interest to use tears as an alternative medium to plasma as it has been proposed with saliva. Nevertheless, significant variations have been observed within and between subjects, thus the use of lachrymal fluid as a plasma substitute should not be recommended [57,92]. In addition, epithelial irritation induces local vasodilatation and promotes exchanges between both mediums (i.e.…”