Abstract

The renal clearance of fluoride (CF) was studied in pentobarbital-anesthetized rats. Urine flow rate and chloride clearance, previously thought to be the main determinants of CF, were readily dissociated from CF. Neither the clearance of sodium nor the excretion of potassium correlated consistently with CF. In experiments designed to manipulate urinary pH, viz., the administration of NaHCO3 or NH4Cl, acetazolamide, and mannitol, CF correlated closely with urinary pH. At a urinary pH of 5.0-k96, CF/GFR averaged less than 5%, while at a urinary pH of approximately 7.6, mean CF/GFR exceeded 65%. The data suggest that 35-45% of the filtered fluoride is reabsorbed in the proximal tubule, regardless of the final urinary pH, while in acidosis the majority of fluoride reabsorption occurs in the distal nephron. The results suggest that the tubular reabsorption of fluoride is inversely related to tubular fluid pH. Fluoride reabsorption seems to occur by nonionic diffusion, apparently as hydrogen fluoride. Depending on local pH gradients, it may occur along the entire nephron.

• Related Studies :

  • Intake and metabolism of fluoride

    The purpose of this paper is to discuss the major factors that determine the body burden of inorganic fluoride. Fluoride intake 25 or more years ago was determined mainly by measurement of the concentration of the ion in the drinking water supply. This is not necessarily true today because of

  • Fluoride pharmacokinetics during acid-base balance changes in man

    Five healthy subjects were each given fluoride 3.0 mg (F) as sodium fluoride tablets on two occasions - during production of acid urine, induced by giving NH4Cl, and during production of alkaline urine obtained by giving NaHCO3. Frequent plasma and urine samples were taken up to 12 h and were

  • Plasma and developing enamel fluoride concentrations during chronic acid-base disturbances

    Mild acid-base disturbances were induced in rats for 30 days. These disturbances did not affect % ash of maxillary incisors or % P of the developing enamel from mandibular incisors. Total fluoride intake (food and water) among groups drinking fluoride-free water was constant. Nevertheless, average plasma and developing enamel fluroide

  • Fluoride metabolism

    Knowledge of all aspects of fluoride metabolism is essential for comprehending the biological effects of this ion in humans as well as to drive the prevention (and treatment) of fluoride toxicity. Several aspects of fluoride metabolism - including gastric absorption, distribution and renal excretion - are pH-dependent because the coefficient

  • Environmental and physiological factors affecting dental fluorosis

    In addition to differences in fluoride intake and possibly to calcium deficiency or malnutrition, there are several factors which may account for individual differences in the occurrence of dental fluorosis. Disorders in acid-base balance affect the renal handling of fluoride such that, in acidosis, the excretion rate is diminished and,

• Related FAN Content :

  • Fluoridation, Dialysis & Osteomalacia

    In the 1960s and 1970s, doctors discovered that patients receiving kidney dialysis were accumulating very high levels of fluoride in their bones and blood, and that this exposure was associated with severe forms of osteomalacia, a bone-softening disease that leads to weak bones and often excruciating bone pain. Based on

  • Dental Fluorosis & Enamel Hypoplasia in Children with Kidney Disease

    Children with kidney disease are known to have high levels of fluoride in their blood and to be at risk for disfiguring tooth defects. Research suggests that high levels of fluoride in blood, which can cause the tooth defect known as dental fluorosis, can contribute to the defects that occur

  • Fluoride Exposure Aggravates the Impact of Iodine Deficiency

    A consistent body of animal and human research shows that fluoride exposure worsens the impact of an iodine deficiency. Iodine is the basic building block of the T3 and T4 hormones and thus an adequate iodine intake is essential for the proper functioning of the thyroid gland. When iodine intake is inadequate during infancy and

  • Skeletal Fluorosis & Individual Variability

    One of the common fallacies in the research on skeletal fluorosis is the notion that there is a uniform level of fluoride that is safe for everyone in the population. These "safety thresholds" have been expressed in terms of (a) bone fluoride content, (b) daily dose, (c) water fluoride level, (d) urinary fluoride level, and (e) blood fluoride level. The central fallacy with each of these alleged safety thresholds, however, is that they ignore the wide range of individual susceptibility in how people respond to toxic substances, including fluoride.

  • Factors which increase the risk for skeletal fluorosis

    The risk for developing skeletal fluorosis, and the course the disease will take, is not solely dependent on the dose of fluoride ingested. Indeed, people exposed to similar doses of fluoride may experience markedly different effects. While the wide range in individual response to fluoride is not yet fully understood, the following are some of the factors that are believed to play a role.