| Abstrakt: |
Objectives: The catalytic α subunit of the sodium-potassium ATPase, the target of digitalis glycosides, has three isoforms is tissuespecific and developmentally regulated. While the effect of pressure overload on Na, K-ATPase isoform expression has been studied in rodent heart, there are no systematic data on this question in hearts of larger animals, which differ from those of rodents both in isoform composition and in glycoside sensitivity. Thus, we investigated the expression of Na, K-ATPase isoforms in normal dog heart; we also examined the effect of experimental left ventricular hypertrophy on isoform expression. Methods: hypertrophy was produced by aortic banding. Expression was assessed by quantitative Northern and Western blotting, immuno-fluorescence, andH-ouabain binding. Results: RNA blotting indicated that the α3 isoform represented 11% of Na, K-ATPase mRNA in normal dog LV. Normal dog LV expressed α1 and α3 protein, but no detectable α2; immunoreactive α1 and α3 protein were also present in Purkinje fibers. There was a statistically significant decrease in total expression of all α isoform mRNA's in hypertrophied dog LV, resulting in a greater proportion of α1. The expression level of the α3 isoform mRNA and protein was lower in hypertrophied hearts. Conclusions: These results indicate a greater proportion of α1 isoform pumps in experimental canine hypertrophy. Thus, shifts in Na, K-ATPase isoforms occur in pressure-overloaded heart in large animals as well as rodents. [ABSTRACT FROM AUTHOR] |
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