Dexamethasone blocks adaptive increase of Na+-Pi cotransport in renal brush border membrane elicited by thyroid hormone.
Dexamethasone administered to rats blocks and/or reverses adaptive increases in the rate of Na+-Pi cotransport, and also in the Na+-dependent binding of [14C]-phosphonoformic acid (PFA) by renal brush border membrane (BBM) vesicles elicited by thyroid hormone (T3). In contrast, dexamethasone had no effect on Na+-independent binding of [14C]-phosphonoformic acid, on Na+-dependent transport of D-glucose or on Na+-dependent binding of phlorizin by BBMV which indicates that its inhibitory effect is specific for Na+-Pi cotransport system of BBM. These findings suggest that glucocorticoids antagonize T3-elicited adaptive enhancement of Na+-Pi cotransport in renal proximal tubules by blocking the T3-stimulated de novo synthesis of Na+-Pi symporters and/or their insertion into BBM.
Yusufi
A N
AN
Nephrology Research Unit, Mayo Clinic and Foundation Rochester, MN 55905.
Moltaji
H
H
Dousa
T P
TP
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D017245:Foscarnet; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D010280:Parathyroid Glands / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D013965:Thyroidectomy; D014284:Triiodothyronine / Q000494:pharmacology*
D002352:Carrier Proteins; D010710:Phosphates; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D014284:Triiodothyronine; D017245:Foscarnet; D003907:Dexamethasone; D010746:Phosphonoacetic Acid