The induction of apoptosis by contrast media (CM) and mannitol (M) was inve
stigated in the hearts and kidneys of 12-mo-old male SHR rats. Ten groups o
f 3 SHR rats received a dose of 5 ml/kg of one of the following: Hypaque (H
)-30, H-60, H-76, Omnipaque (O)-140, O-350, mannitol (M)-4%, M-9%, M-19%, M
-27%, or saline (S). DNA fragmentation was detected using the terminal deox
ynucleotidyl transferase-mediated [TdT] dUTP nick-end labeling (TUNEL) meth
od, and the morphology characteristics of apoptosis were confirmed in cardi
ac and renal cells. The immunoreactivities of Bcl-2, Bar, and p53 were asse
ssed immunohistochemically in the kidneys. Apoptosis occurred in cardiac my
ocytes and renal tubular and glomerular cells as well as in vascular endoth
elial and smooth muscle cells of the heart and kidneys. The high frequency
of apoptosis correlated significantly with the increase in the osmolality o
f the H, O, and hi. The increased Bax, the increased p53, and the decreased
Bcl-2 immunoreactivities were detected in H- or O-treated, but not in M-tr
eated, rats. These findings suggest that CM and M activate cardiac and rena
l apoptosis by different mechanisms and that the apoptotic process may be i
mplicated in acute heart and renal damage.