K. Kato et al., Changes in the expression of cardiac Na+-K+ ATPase subunits in the UM-X7.1cardiomyopathic hamster, LIFE SCI, 67(10), 2000, pp. 1175-1183
Previous studies have shown that cardiac Na+-K+ ATPase activity in the UM-X
7.1 hamster strain is decreased at an early stage of genetic cardiomyopathy
and remains depressed; however, the mechanism for this decrease is unknown
. The objective of the present study was to assess whether changes in the e
xpression of cardiac Na+ -K+ ATPase subunits in control and UM-X7.1 cardiom
yopathic hamsters are associated with alterations in the enzyme activity. A
ccordingly, we examined sarcolemmal Na+-K+ ATPase activity as well as prote
in content and mRNA levels for the alpha(1), alpha(2), alpha(3), and beta(1
)-subunit of the Na+-K+ ATPase in 250-day-old UM-X7.1 and age-matched, cont
rol Syrian hamsters; this age corresponds to the severe stage of heart fail
ure in the UM-X7.1 hamster. Na+-K+ ATPase activity in UM-X7.1 hearts was de
creased compared to controls (9.0 +/- 0.8 versus 5.6 +/- 0.8 mu mol Pi/mg p
rotein/hr), Western blot analysis revealed that the protein content of Na+-
K+ ATPase alpha(1)- and beta(1)-subunits were increased to 164 +/- 27% and
146 +/- 22% in UM-X7.1 hearts respectively, whereas that of the or,and alph
a(3)-subunits were decreased to 82 +/- 5% and 69 +/- 11% of control values.
The results of Northern blot analysis for mRNA levels were consistent with
the protein levels; mRNA levels for the alpha(1)- and beta(1)-subunits in
UM-X7.1 hearts were elevated to 165 +/- 14% and 151 +/- 10%, but the alpha(
2)-subunit was decreased to 60 +/- 8% of the control value. We were unable
to detect mRNA for the alpha(3)-subunit in either UM-X7.1 or control hearts
. These data suggest that the marked depression of Na+-K+ ATPase activity i
n UM-X7.1 cardiomyopathic hearts may be due to changes in the expression of
subunits for this enzyme. (C) 2000 Elsevier Science Inc. All rights reserv
ed.