INCREASED SINUSOIDAL WALL PERMEABILITY AND LIVER FATTY CHANGE AFTER 23 HEPATECTOMY - AN ULTRASTRUCTURAL-STUDY IN THE RAT/

Accumulation of lipids in the hepatocyte cytoplasm after partial hepat ectomy (PH) has long been recognized, but the mechanism behind this ph enomenon is still poorly understood. In this study, rats subjected to a standard two-thirds PH showed early and marked increase in portal ve nous pressure (P < .01). On scanning electron microscopy, the regenera ting liver fixed by por tal perfusion under hemodynamic conditions ide ntical to that found in vivo during the first 24 hours showed a signif icant (P < .01) 10-fold increase in the sinusoidal wall porosity (perc entage open area by fenestrations). This was paralleled by the disappe arance of the sieve-plate arrangement of small fenestrations and by a significant decrease in the number of fenestrations per micrometers sq uared of sinusoidal surface at 6 (P < .01) and 12 hours (P < .05). In addition, there were major changes in the frequency and distribution o f all three classes of fenestrations. At 6 and 12 hours, there was a m arked decrease of small class 1 fenestrations and a marked increase of intermediate class 2 fenestrations and large class 3 fenestrations (P > .0001). A concurrent accumulation of lipid droplets in the hepatocy te cytoplasm produced a 20-fold increase in the hepatocyte total lipid volume. A statistically significant linear correlation (r = 0.907; P < .01) was found between the amount of intracellular lipids and the da ta quantitating the changes in porosity of liver sinusoids at 24 hours . It is concluded that an increased sinusoidal wail permeability to li pids may be the primum movens in the pathogenesis of transient liver f atty change after PH in the rat.