Morphology, ultrastructure, and function of hepatocytes during liver drug metabolism

Ultrastructure of in situ perfusion-fixed avian liver, with special reference to structure of the sinusoids

Broiler chicken and laying hen livers were fixed using a simple technique of in situ puncture perfusion of cacodylate-buffered fixative, which allowed characterisation of the fine structure of hepatic parenchyma, hepatocytes, bile ductules, and, in particular, the sinusoidal cells including endothelial, Kupffer, and Ito cells. Sinusoidal endothelial cells with their bulging perinuclear cytoplasm, evident in both transmission and scanning electron micrographs, were easily distinguishable from Kupffer cells, which possessed numerous pseudopodia. Bile ductular epithelium and hepatocytes of the laying hens contained large amounts of lipid. The ultrastructural characteristics of intercalated cells (putative extra-sinusoidal macrophages of chicken liver) are described and their possible role as precursors of Kupffer cells is discussed.

Ethinylestradiol increases volume and decreases sinusoidal membrane surface in the rat liver: a stereological analysis

Structural alterations of liver parenchyma caused by ethinylestradiol, a synthetic estrogen known to induce cholestasis and to act as a tumor promoter factor, were investigated. Male rats treated with 17 alpha-ethinylestradiol (5 mg/kg body weight for 5 days) were compared with controls (n = 5 each). After perfusion fixation and systematic random sampling, paraffin sections, semithin sections and thin sections were examined observing standard stereological techniques. Ethinylestradiol treatment induced an increase in liver volume by 65% (p less than 0.001), which was caused more by hypertrophy (volume of singular hepatocyte +35%, p less than 0.001) than by hyperplasia (number of hepatocytes +23%, p less than 0.001). A decrease in sinusoidal membrane surface density (-43%, p less than 0.005) associated with a decrease in sinusoidal microvillar volume density (-50%, p less than 0.005) were both compensated for by the increase in liver volume. No canalicular alterations were observed. Thus changes in hepatocytes detectable with stereological techniques affect the sinusoidal pole where decreased sinusoidal membrane surface is associated with or reflects a substantial loss of membrane phospholipids. The increased liver volume may constitute an adaptive response compensating for the relative decrease in sinusoidal membrane surface and displays characteristics comparable to those of preneoplastic hepatocytes.

The influence of buffers during fixation on the appearance of smooth endoplasmic reticulum and glycogen in hepatocytes of normal and glycogen-depleted rats

Liver tissue of normal and glycogen depleted rats was prepared for transmission electron microscopy by perfusion fixation and subsequent osmication in the presence of various buffers, dehydration in aethanol and embedding in epon. The use of Na/K-phosphate or Na-cacodylate to buffer glutaraldehyde led to similar appearance and distribution of SER. When Na-cacodylate was used during osmication, more SER membranes were retained but less accumulations of glycogen were found than after osmication in the presence of Na/K-phosphate. Fixation with s-collidine buffered osmium led to an easily recognisable network of SER comprising wide tubules whereas glycogen was hindered to be stained. Veronal acetate or Na-cacodylate supplemented with sucrose resulted in marked dilation and disintegration of SER. A similar effect was obtained when Na/K-phosphate or Na-cacodylate was used in hyposmolar concentration as buffer for glutaraldehyde. Liver of fasted rats or glucagon-treated rats after perfusion with Na/K-phosphate buffered glutaraldehyde and osmication in the presence of Na/K-phosphate or Na-cacodylate comprised glycogen-depleted hepatocytes which contained abundant SER membranes occupying the entire space between other organelles even in samples harvested 3 h after glucagon administration. The diversity in appearance and distribution of SER and glycogen granules, which depends to a large extend on the buffer used, suggests that SER membranes may not be sufficiently stabilized during aldehyde fixation and osmication. We thus consider it likely that large accumulations of glycogen granules are the consequence of disintegration of SER membranes during processing rather than they represent the morphologic substrate of physiological degradation of SER membranes in the course of glycogen synthesis and deposition.

Hepatocellular peroxisomes in human alcoholic and drug-induced hepatitis: a quantitative study

The peroxisomes in the liver of four patients with alcoholic hepatitis and in six patients with drug-induced hepatitis are compared to eight control livers by catalase cytochemistry and morphometry. A decrease of catalase activity is observed in alcoholic, amitriptyline, aprindine, clomipramine and methiomazole hepatitis. Peroxisomes with a heterogeneous distribution of the catalase reaction product are found in most hepatitis livers. The number of organelles is increased 1.5 to 4.2 times in alcoholic, aprindine, methimazole and phenytoin hepatitis livers. In the last case, peroxisomes are also smaller. Changes in shape are seen in all hepatitis livers; they include invaginations, tails, funnel-like constrictions and gastruloid cisternae. In aprindine, phenytoin, methimazole and two alcoholic hepatitis livers, surface density exceeds the upper control value. These data indicate a loss of catalase activity in most hepatitis livers but also peroxisomal proliferation and shape modifications. It has been proposed that the latter changes are favorable for metabolic activity.

Comparative biochemical and morphometric changes associated with induction of the hepatic mixed function oxidase system in the rat

This study characterized the induction of the rat hepatic cytochrome P-450-dependent mixed function oxidase system by SK&F 86002 [6-(4'-fluorophenyl)-5-(4'-pyridyl)-2,3-dihydroimidazo-(2,1-b)thia zole], an inhibitor of both the cyclooxygenase and 5-lipoxygenase pathways of arachidonic acid metabolism. The induction characteristics of SK&F 86002 were compared to those of the classical inducer, phenobarbital, and morphological features of both SK&F 86002 and phenobarbital induced hepatocellular hypertrophy were quantitated. Rats were administered either SK&F 86002 (6, 18, or 60 mg/kg/day, po) or phenobarbital (8, 24, 80 mg/kg/day, ip) for 3 or 14 consecutive days. Liver to body weight ratio, total hepatic microsomal protein and cytochrome P-450 content, ethoxycoumarin-O-deethylase (ECOD) and leukotriene B4(LTB4) omega- and omega-1 hydroxylase were measured. Ultrastructural morphometry of the liver from control, and high dose SK&F 86002 (60 mg/kg/day) and phenobarbital (80 mg/kg/day) treated rats was completed. On day 3, phenobarbital increased liver to body weight ratio but only at the 80 mg/kg/day dosage; microsomal protein content was unchanged. ECOD activity increased in a dose-dependent fashion. LTB4 omega- and omega-1 hydroxylase activities were unaffected. Administration of SK&F 86002 for 3 days increased the liver to body weight ratio at both the 18 and 60 mg/kg/day dosage; microsomal protein content was unchanged. ECOD activity was significantly increased by the 60 mg/kg/day dosages of SK&F 86002. On day 14, phenobarbital increased the liver to body weight ratio and microsomal protein content but again only at the 80 mg/kg/day dosage. Cytochrome P-450 content was increased by all dosages.(ABSTRACT TRUNCATED AT 250 WORDS)