Regulation by Glucocorticoids of Expression and Activity of rBSC1, the Na+-K+(NH4+)-2Cl−Cotransporter of Medullary Thick Ascending Limb
| Autor: | Catherine Vernimmen, Xavier Belenfant, Maurice Bichara, Valérie Sibella, Amel Attmane-Elakeb, Steven C. Hebert |
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| Rok vydání: | 2000 |
| Předmět: |
Male
Vasopressin medicine.medical_specialty Arginine Sodium-Potassium-Chloride Symporters Intracellular pH Stimulation Biology Biochemistry Dexamethasone Rats Sprague-Dawley Glucocorticoid receptor Internal medicine medicine Animals RNA Messenger Molecular Biology Kidney Medulla Kidney Adrenalectomy Cell Biology Rats Arginine Vasopressin Quaternary Ammonium Compounds Kidney Tubules medicine.anatomical_structure Endocrinology Carrier Proteins Cotransporter hormones hormone substitutes and hormone antagonists medicine.drug |
| Zdroj: | Journal of Biological Chemistry. 275:33548-33553 |
| ISSN: | 0021-9258 |
| Popis: | To assess whether glucocorticoids regulate rBSC1, the apical Na(+)-K(+)(NH(4)(+))-2Cl(-) cotransporter of kidney medullary thick ascending limb (MTAL), studies were performed in normal rats, adrenalectomized (ADX) rats, and ADX rats infused with dexamethasone for 6 days. The effects of dexamethasone on rBSC1 were also studied in vitro using isolated rat MTAL segments. Cotransport activity was estimated by intracellular pH measurements; rBSC1 protein was quantified in MTAL crude membranes by immunoblotting analysis, and mRNA was quantified by quantitative reverse transcription-polymerase chain reaction. The abundance of rBSC1 protein and mRNA increased in ADX rats infused with dexamethasone compared with ADX rats (p < 0. 04). In addition, application of dexamethasone for 1-3 h to MTALs caused rBSC1 protein and mRNA abundance and cotransport activity to significantly increase in a hyperosmotic medium (450 mosmol/kg of H(2)O) containing 0.7 nm arginine vasopressin, which is an in vitro experimental condition that resembles the in vivo MTAL environment. Results obtained in various media and with 8-bromo-cAMP indicated that stimulation of rBSC1 expression by glucocorticoids required interactions between glucocorticoid receptor- and cAMP-dependent factors. Up to 100 nm d-aldosterone had no effect on cotransport activity in vitro. Thus glucocorticoids directly stimulate MTAL rBSC1 expression and activity, which contributes to glucocorticoid-dependent effects on the renal regulation of acid-base balance and urinary concentrating ability. |
| Databáze: | OpenAIRE |
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