AJP - Renal Physiology, Vol 232, Issue 4 335-F340, Copyright © 1977 by American Physiological Society
Effect of sodium fluoride on concentrating and diluting ability in the rat
J. D. Wallin and R. A. Kaplan
Mechanisms for the concentrating defect produced by fluoride were examined
in the rat. Free-water clearance at all levels of delivery was normal after
5 days of chronic fluoride administration in the hereditary hypothalamic
diabetes insipidus rat. In the Sprague-Dawley rats, during moderate
fluoride administration (120 micronmol/kg per day), urine osmolality and
cyclic AMP excretion decreased and urine volume increased, but after
exogenous vasopressin, volume decreased and osmolality and cyclic AMP
increased appropriately. During larger daily doses of fluoride (240
micronmol/kg per day) urinary osmolality and cyclic AMP decreased and
volume increased, which was similar to the changes seen during lower
fluoride dosages, but these parameters did not change after exogenous
vasopressin. These data suggest that ascending limb chloride reabsorption
is unaltered by fluoride administration; in the presence of sufficient
fluoride, collecting tubular cells apparently do not generate cyclic AMP or
increase permeability appropriately in response to vasopressin. The
postulated defect is felt to be due to either a decrease in ATP
availability or to a direct inhibitory effect of fluoride on the
vasopressin-dependent cyclic AMP generating system.
