Background A cardiac angiotensin Ii-generating system has been suspect
ed to be involved in various cardiac pathological conditions, Both ang
iotensin converting enzyme and human chymase can convert angiotensin I
to angiotensin II, Objective To clarify the relative contributions of
these two enzymatic pathways to angiotensin II generation in vivo. Me
thods We assessed the expression levels of messenger RNA (mRNA) for co
llagen type I alpha, transforming growth factor-beta(1), brain natriur
etic peptide, angiotensin converting enzyme and chymase in right atria
l appendages by competitive polymerase chain reaction and Northern blo
t analyses, Correlations among the concentrations of these mRNA were a
nalysed to obtain insight that might be important in understanding the
formation of angiotensin II in atrial tissue,Results The collagen typ
e I alpha and brain natriuretic peptide mRNA concentrations were corre
lated significantly to the mean pulmonary arterial pressure, Multivari
ate regression analysis revealed that the collagen type I alpha. mRNA
concentration could be explained in terms of the brain natriuretic pep
tide (P = 0.0005) and angiotensin converting enzyme (P= 0.0084) mRNA c
oncentrations (r = 0.598, P< 0.0001), The chymase mRNA concentration h
ad no significant correlation to the collagen type I alpha. mRNA conce
ntration. Moreover, multiple regression analysis revealed that the tra
nsforming growth factor-beta(1) mRNA concentration could be explained
in terms of the angiotensin converting enzyme mRNA concentration alone
(r = 0.424, P = 0.014), Conclusions The present results suggest that
the level of angiotensin converting enzyme affects the tissue angioten
sin II level in human atria; however, we could obtain no evidence that
chymase is important in determining the tissue angiotensin II level.