title: Thyroid hormones increase Na+-H+ exchange activity in renal brush border membranes.
abstract: Na+-H+ exchange activity, i.e., amiloride-sensitive Na+ and H+ flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na+-H+ exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na+ uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na+ uptake in vesicles from hyperthyroid animals. Na+-dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na+-dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na+ in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na+ reabsorption. Further, the regulation of transtubular Na+ flux has now been shown to be concomitant with modulation of the entry of Na+ into the tubular cell across its luminal membrane, mediated by the exchange reaction, and with the previously reported control of the pumping of Na+ out of the cell across its basolateral membrane, mediated by the Na+,K+-ATPase.
authors.forename: J
authors.initials: J
authors.lastname: Kinsella
authors.forename: B
authors.initials: B
authors.lastname: Sacktor
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006980:Hyperthyroidism / Q000378:metabolism*; D007037:Hypothyroidism / Q000378:metabolism*; D007672:Kidney Cortex / Q000648:ultrastructure*; D008297:Male; D008871:Microvilli / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D011392:Proline / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D017923:Sodium-Hydrogen Exchangers; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D002352:Carrier Proteins; D010710:Phosphates; D017923:Sodium-Hydrogen Exchangers; D014284:Triiodothyronine; D011392:Proline; D005947:Glucose; D013974:Thyroxine