THE ROLE OF GUANINE-NUCLEOTIDE-BINDING PROTEINS IN HAMSTERS WITH MYOCARDIAL HYPERTROPHY

To clarify the role of the guanine nucleotide binding proteins (G-prot eins) in the pathogenesis of myocardial hypertrophy, we investigated t he alterations in myocardial G proteins in 20-week-old F1b hamsters wi th pressure overload induced for 3 days (3-day AS), 7 days (7-day AS) and 14 days (14-day AS) by the stenosis of the abdominal aorta, and in 4- and 20 week-old BIO 14.6 Syrian hamsters (4-wk and 20-wk BIG) with genetic myocardial hypertrophy. The hearts of 7-day AS, 14-day AS and 20-wk BIO with left ventricular hypertrophy exhibited a decrease in t he mRNA levels detected by Northern blot analysis and protein levels o f G protein detected by Western blot analysis as compared with sham-op erated and age-matched F1b hearts. The function of Gs or Gi showed a c oncomitant reduction in both models of myocardial hypertrophy. The hea rts of 3-day AS and 4-wk BIO without myocardial hypertrophy showed no changes in G proteins as compared with sham-operated and age-matched F 1b hearts. These results suggest that a decrease in G proteins is not involved in the pathogenesis of myocardial hypertrophy, but that myoca rdial hypertrophy reduced the G proteins.