Inhibition of arginine vasopressin-stimulated Na+ K+ ATPase activity by difluoromethyl ornithine in the rat renal medulla.
Arginine vasopressin (AVP) stimulates Na+ K+ ATPase and ornithine decarboxylase (ODC) activity in the rat medullary thick ascending limb. The effect of difluoromethyl ornithine (DFMO), a specific inhibitor of ODC activity, on AVP-stimulated Na+ K+ ATPase activity was evaluated using a cytochemical bioassay. Peaks in Na+ K+ ATPase activity in cultured rat renal segments which occurred after tissue had been exposed to 1 fmol AVP/l were completely inhibited by the addition of 20 mmol DFMO/l to the culture medium containing AVP. The addition of 20 mmol DFMO/l to the culture medium containing AVP in the concentration range 0.001-10 fmol/l inhibited completely the stimulation of Na+ K+ ATPase activity by AVP. The response of Na+ K+ ATPase to increasing doses of ATP (10-40 g polypeptide/l) was not influenced by the addition of 20 mmol DFMO/l to the culture medium containing AVP, suggesting that the prevention of AVP-stimulated Na+ K+ ATPase activity by DFMO was not due to a direct effect on the enzyme.
Charlton
J A
JA
Department of Medicine, New Medical School, Newcastle upon Tyne.
Baylis
P H
PH
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D000518:Eflornithine / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007679:Kidney Medulla / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013997:Time Factors
D001127:Arginine Vasopressin; D000255:Adenosine Triphosphate; D000254:Sodium-Potassium-Exchanging ATPase; D000518:Eflornithine