Modulatory effect of some steroid hormones, their glucuronides and ouabain-like compounds on Cavia cobaya kidney Na+,K(+)-ATPase activity.
1. Ouabain-like compounds (approx. mol. wt 700, 2,000 and 4,000 Da) were purified from plasma of essential hypertensive patients. 2. Dose-response experiments performed with (a) steroid hormones, (b) their glucuronides and (c) ouabain-like compounds, emphasize a modulatory effect [activation of the Na,K-ATPase at very low concentrations of ligand, inhibition at higher levels; apparent Ki: (a) between 1 and 0.5 mM; (b) between 1 and 0.5 microM; and (c) between 10 and 1 nM; maximum enhancement of the enzymatic activity: (a) +20%; (b) +45%; and (c) +100%]. 3. Displacement experiments of [3H]ouabain evidence a high competition of the ligands towards the cardioglycoside. The relative I50s are: (a) between 1 and 0.5 mM; (b) between 10 and 1 microM; and (c) between 10 and 0.01 nM.
Giunta
C
C
Dipartimento di Biologia Animale, Università di Torino, Italy.
Ferrero
P
P
Pizzuto
M
M
Cavaletto
M
M
Pessione
E
E
Bracchino
P
P
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005965:Glucuronates / Q000494:pharmacology; D006168:Guinea Pigs; D006728:Hormones / Q000502:physiology*; D006973:Hypertension / Q000097:blood; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000201:enzymology*; D008024:Ligands; D010042:Ouabain / Q000031:analogs & derivatives / Q000494:pharmacology*; D011506:Proteins / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*; D013256:Steroids / Q000502:physiology*
D005965:Glucuronates; D006728:Hormones; D008024:Ligands; D011506:Proteins; D013256:Steroids; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase