Relationship between plasma and tear fluoride levels in rabbit and man
Related Experiment Videos
1Department of Oral Biology-Physiology, Medical College of Georgia, Augusta.
Abstract:
Tear fluoride concentrations were determined in rabbits and man. Tear fluoride levels in reflex tears were higher in rabbits (2-10 mumol/l) than in man (1.4-4 mumol/l), while plasma levels were quite similar in both species (1.5-4 mumol/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 plasma:tear ratio remained constant despite a 2-fold increase in plasma fluoride.
Insights
Fluoride levels in tears differ between rabbits and humans. Chronic fluoride intake increased plasma fluoride in rabbits but not tear fluoride, altering the plasma-to-tear ratio.
Area of Science:
- Ophthalmology
- Toxicology
- Biochemistry
Background:
- Fluoride is essential for dental health but can be toxic at high concentrations.
- Understanding fluoride distribution in ocular tissues is crucial for assessing potential toxicity.
- Tear and plasma fluoride levels provide insights into systemic and local fluoride exposure.
Purpose of the Study:
- To compare tear and plasma fluoride concentrations in rabbits and humans.
- To investigate the effects of chronic and acute fluoride ingestion on tear and plasma fluoride levels.
- To determine the relationship between plasma and tear fluoride concentrations under different exposure conditions.
Main Methods:
- Measurement of fluoride concentrations in tears and plasma.
- Administration of varying concentrations of fluoride in drinking water to rabbits over 29 days.
- Administration of acute fluoride doses to human subjects.
- Calculation of plasma to tear fluoride ratios.
Main Results:
- Rabbits exhibited higher reflex tear fluoride concentrations (2-10 mumol/l) than humans (1.4-4 mumol/l).
- Plasma fluoride levels were similar between species (1.5-4 mumol/l).
- Chronic fluoride ingestion in rabbits led to a dose-dependent increase in plasma fluoride but not tear fluoride, significantly increasing the plasma:tear ratio.
- Acute fluoride ingestion in humans increased both plasma and tear fluoride, maintaining a constant plasma:tear ratio.
Conclusions:
- Tear fluoride levels do not directly mirror plasma fluoride levels, particularly under chronic exposure conditions.
- Species differences exist in tear fluoride concentrations.
- The plasma:tear fluoride ratio is a dynamic indicator influenced by the duration and level of fluoride exposure.