Endogenous renal dopamine production regulates phosphate excretion.
We examined the effect of endogenous dopamine production on Pi and citrate excretion by Wistar rats. Carbidopa (20-40 mumol/kg ip) decreased dopamine, Pi, and citrate excretion within 20 min (86%, 47%, and 38%, respectively); Pi reabsorption increased 11 +/- 4% (P = 0.03). The decreases were sustained for at least 18 h. 3-Hydroxybenzylhydrazine (45 mumol/kg ip) reduced Pi excretion 24%. Benserazide (40 mumol/kg ip and 0.1 mumol/min iv) reduced dopamine excretion (94%) and blocked the effect of carbidopa on Pi and citrate excretion. In isolated perfused kidneys benserazide, carbidopa, and 3-hydroxybenzylhydrazine all decreased Pi excretion. Dopamine (1 mumol/l) added to cortical minceates reduced brush-border membrane vesicle (BBMV) 32P uptake by 8% (P < 0.02) and amiloride-inhibitable 22Na uptake by 19%. Carbidopa added to minceates increased 32P uptake by 12%. Carbidopa pretreatment increased (75%) amiloride-sensitive 22Na uptake into BBMV of rats fed a high-salt diet. Uptake was not increased into BBMV from rats fed a low-salt diet. Carbidopa increased (17%) basolateral membrane Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) gradually over 4 h. Na(+)-K(+)-ATPase did not increase in rats fed a low-phosphorous diet, but did increase when dopa was added to the diet. Thus endogenous dopamine appears to directly control Na(+)-Pi and Na+/H+ transport and secondarily alter basolateral membrane Na(+)-K(+)-ATPase.
Debska-Slizien
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Department of Clinical Biochemistry, University of Toronto, Ontario, Canada.
Ho
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Drangova
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Baines
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AD
D000818:Animals; D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D002230:Carbidopa / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002951:Citrates / Q000652:urine; D019343:Citric Acid; D004032:Diet; D004298:Dopamine / Q000096:biosynthesis*; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D010477:Perfusion; D010710:Phosphates / Q000008:administration & dosage / Q000494:pharmacology / Q000652:urine*; D051381:Rats; D017208:Rats, Wistar; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D027981:Symporters
D065105:Aromatic Amino Acid Decarboxylase Inhibitors; D002352:Carrier Proteins; D002951:Citrates; D010710:Phosphates; D017923:Sodium-Hydrogen Exchangers; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D019343:Citric Acid; D000254:Sodium-Potassium-Exchanging ATPase; D002230:Carbidopa; D004298:Dopamine