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Sodium pump isoform specificity for the digitalis-like factor isolated from human peritoneal dialysate
Q F Tao1, N K Hollenberg, D A Price
1Department of Medicine, Harvard Medical School, Brigham and Women's Hospital, Boston, Mass. 02115, USA.
Hypertension (Dallas, Tex. : 1979)
|March 1, 1997
Summary
Researchers identified a novel sodium pump inhibitor in renal failure patients. This endogenous factor differs from ouabain in its potent inhibition of multiple sodium pump alpha-isoforms, particularly alpha2.
Area of Science:
- Biochemistry
- Physiology
- Nephrology
Background:
- Volume expansion in renal failure is linked to endogenous digitalis-like factors.
- These factors may influence cardiovascular regulation and sodium pump activity.
Purpose of the Study:
- To characterize the inhibitory profile of a labile digitalis-like factor (DLF) against Na,K-ATPase alpha-isoforms.
- To compare the DLF's inhibitory effects with those of ouabain.
Main Methods:
- Preparation of microsomal Na,K-ATPase from rat kidney (alpha1), skeletal muscle (alpha2), and fetal brain (alpha3).
- Assessment of inhibition by DLF and ouabain using Northern and Western blot analyses and enzyme activity assays.
Main Results:
- Ouabain significantly inhibited alpha2 and alpha3 isoforms but minimally affected alpha1.
- The DLF markedly inhibited kidney (alpha1) and skeletal muscle (alpha2) isoforms, with moderate inhibition of fetal brain (alpha3).
- DLF demonstrated concentration-dependent inhibition of alpha2 and alpha3 isoforms, unlike ouabain.
Conclusions:
- The labile digitalis-like factor exhibits a distinct inhibitory profile compared to ouabain.
- DLF effectively inhibits all three Na,K-ATPase alpha-isoforms, especially alpha2, suggesting unique physiological roles.