When acetaminophen (25mM) was introduced into the perfused rat liver, the hepatic O2 uptake was rapidly inhibited first and then later slow-down. The rapid inhibition was found to be due to mitochondrial blockade, whereas the so-called slow inhibition" was associated with microcirulatory aberrations as evidenced by inhomogneous staining of the liver tissue by trypan blue infusion (0.1%). NaCN (0.5mM) also caused rapid and slow respiratory inhibitions, giving heterogeneous trypan blue staining.ning.