Spyridon D. Skaltsas

Induction of metallothionein in the liver of carbon tetrachloride intoxicated rats: an immunohistochemical study.

Metallothioneins (MTs), are low molecular weight proteins, mainly implicated in metal ion detoxification. In the present study, we investigated the expression of hepatic MT in a rat model of injury and regeneration, induced by carbon tetrachloride (CCl(4)) administration. A single intraperitoneal injection of 1 ml CCl(4)/kg body weight was performed in male Wistar rats, killed at different time points post-administration. The enzymatic activities of aspartate and alanine aminotransferases in serum were determined, in addition to the liver histological findings, to estimate hepatotoxicity. The rate of tritiated thymidine incorporation into hepatic DNA, the enzymatic activity of thymidine kinase in liver tissue and the assessment of the mitotic index in hepatocytes, were used as indices of regeneration. MT was detected immunohistochemically in liver tissue sections. CCl(4) administration caused severe hepatic injury, followed by regeneration. MT expression became prominent as early as 12 h after the administration of CCl(4), in the nuclei of hepatocytes, while at 24 and 36 h intense cytoplasmic staining for MT appeared in the hepatocytes in the vicinity of necrotic areas. The peak of hepatocyte proliferative capacity, occurring at 48 h post-CCl(4) administration coincides with the maximum nuclear and cytoplasmic MT expression. At further time points MT expression presented a decreasing trend. Induction of MT expression was observed in the liver after a single administration of CCl(4), being more prominent at the time of maximum hepatocellular proliferation, participating actively in the replication of hepatocytes.

Effect of serotonin receptor 2 blockage on liver regeneration after partial hepatectomy in the rat liver.

Abstract: The effect of serotonin receptor 2 blockade (5‐HT2) on liver regeneration after 30–34% and 60–70% partial hepatectomy in the rat liver was investigated.

Hepatic stimulator substance administration enhances regenerative capacity of hepatocytes in cadmium-pretreated partially hepatectomized rats.

The liver is of central importance in the metabolism of essential and toxic metals such as cadmium (Cd). Cd pretreatment suppressed the regenerative capacity of hepatocytes, which normally occurs 24 hr after partial hepatectomy, due to the inhibition of the activity of the enzyme thymidine kinase. The effect of hepatic stimulator substance (HSS) administration (10, 20, and 40 mg protein/kg body weight) on hepatocyte proliferation was investigated in Cd-pretreated partially hepatectomized rats. HSS administration partly restored the suppressed hepatocyte DNA biosynthesis in Cd-pretreated partially hepatectomized rats. The hepatocyte mitotic activity and the percentage of proliferating cell nuclear antigen-positive nuclei were in accordance with the liver proliferative status. The administration of HSS did not affect in a statistically significant manner the activity of the enzyme thymidine kinase in Cd-pretreated partially hepatectomized rats. It is suggested that the administration of HSS ameliorates the diminished hepatocyte regenerative response to partial hepatectomy in this model of acute liver injury, due to Cd intoxication.

Effect of Interferon-α2b administration on rat liver regeneration after partial hepatectomy

The purpose of the present study was todelineate the effect of interferon-α2b(IFN-α2b) administration on the liverregenerative capacity after partial hepatectomy in rats.The administration of IFN-α2bsimultaneously with partial hepatectomy did not affect hepatic2b proliferation in a statistically significant manner.When IFN-α2b was administered either 2or 12 hr postoperatively, an inhibition of hepatocyteproliferation was observed 24 hr postoperatively, while atfurther time intervals up to 48 hr, DNA synthesisremained similar to that observed in the simplypartially hepatectomized rats. The enzyme thymidinekinase (TK), has been implicated in the suppression ofproliferation in interferon-treated cell cultures. Inall IFN-α2b-treated groups of rats,alterations of TK activity were observed without beingcorrelated to the liver regenerative status. Additionally,the administration of the polyamine putrescine inpartially hepatectomized rats treated at the time ofsurgery with IFN strongly enhanced TK activity, but did not affect DNA biosynthesis. In theabove-mentioned in vivo model of controlled cellularproliferation, the administration ofIFN-α2b affected the rate of hepatocyteproliferation depending on the time of its administration; this effect was notcorrelated to the enzymatic activity of TK, as inhibitedTK activity is responsible for the suppressed DNAsynthesis in in vitro systems.

Using higher‐order crossings to distinguish liver regeneration indices in hepatectomized diabetic and non‐diabetic rats

Background and Aims:  Diabetes mellitus is implicated in several liver diseases; hence, its potential affection to liver regenerative capacity is an open research question. So far, only sporadic studies have addressed this issue, mainly using basic statistical techniques. The current study evaluated the ability of a novel technique, namely higher‐order crossings (HOC), based on liver DNA biosynthesis and thymidine kinase (TK) enzymatic activity data, to discriminate liver regeneration processes between hepatectomized diabetic and non‐diabetic rats.

Putrescine administration reverses cadmium-associated inhibition of liver regeneration

The liver is of central importance in themetabolism of essential and toxic metals such ascadmium. Cadmium pretreatment suppressed the liverregenerative response to partial hepatectomy, due to theinhibition of the enzymatic activity of thymidine kinase.Exogenous putrescine administration has been reported tostimulate liver regeneration in animal models of acuteliver failure. The purpose of this study was to document whether the administration of thispolyamine enhances the impaired regenerative capacity ofhepatocytes in cadmiumpretreated partiallyhepatectomized rats. The intraperitoneal administration of putrescine (1 or 10 mg/kg body weight), atthe time of surgery and at 4 and 8 hr postoperativelypartly restored the suppressed hepatocytedeoxyribonucleic acid (DNA) biosynthesis and thymidinekinase activity in cadmium-pretreated partiallyhepatectomized rats. Mitotic activity and the percentageof hepatocytes positive for proliferating cell nuclearantigen nuclei were in accordance with the liver proliferative status. Our results showed thatexogenous putrescine administration is able to improvediminished liver regeneration after partial hepatectomyin this animal model of acute hepatic injury.

Liver regeneration: immunohistochemichal study of intrinsic hepatic innervation after partial hepatectomy in rats

BackgroundWe examined the intrinsic hepatic innervation after partial hepatectomy (PH) in rats and the presence and pattern of neural sprouting in regenerating liver.MethodsMale Wistar rats (age 9-13 weeks-w, weight 204-356 g), were submitted to two-thirds PH. Rats were sacrificed at postoperative days (d) 1, 3, 5, 7, at 2 and 4 w, and at 3 and 6 months (m) (6-7 animals/group, control group n = 4). Immunohistochemistry for the pan-neural marker protein gene product 9.5 (PGP9.5) and growth-associated protein 43 (GAP-43), a marker of regenerating nerve axons, was performed on tissue sections from the R1 lobe of the regenerating liver. Portal tracts (PTs) with immunoreactive fibers were counted in each section and computer-assisted morphometric analysis (Image Pro Plus) was used to measure nerve fiber density (number of immuno-positive nerve fibers/mm2 (40x)).ResultsImmunoreactivity for PGP9.5 was positive in all groups. The number of PGP9.5 (+) nerve fibers decreased from 0.32 +/- 0.12 (control group) to 0.18 +/- 0.09 (1d post-PH group), and gradually increased reaching pre-PH levels at 6 m (0.3 +/- 0.01). In contrast, immunoreactivity for GAP-43 was observed at 5d post-PH, and GAP-43 (+) PTs percentage increased thereafter with a peak at 3 m post-PH. GAP-43 (+) nerve fiber density increased gradually from 5d (0.05 +/- 0.06) with a peak at 3 m post-PH (0.21 +/- 0.027). At 6 m post-PH, immunoreactivity for GAP-43 was not detectable.ConclusionsFollowing PH in rats: 1) nerve fiber density in portal tracts decreases temporarily, and 2) neural sprouting in the regenerating liver lobes starts at 5d, reaches peak levels at 3 m and disappears at 6 m post-PH, indicating that the increase in hepatic mass after PH provides an adequate stimulus for the sprouting process.

Effect of acute phase response induction by turpentine oil administration on hepatocyte regeneration after partial hepatectomy in the rat

The aim of the present study was to examine whether acute-phase response induction by turpentine oil administration, affects hepatocyte regeneration after partial hepatectomy (PH) in rats. It is known that administration of turpentine oil in rats induces acute-phase response, with maximum circulation of acute-phase reactants 24 h after the injection. Turpentine oil was injected in rats subcutaneously, either 24 h prior to or simultaneous with 70% PH. The regenerative capacity of hepatocytes was estimated 24 h postoperatively, by the in-vivo incorporation of tritiated thymidine into liver DNA, the enzymatic activity of liver thymidine kinase (TK), the mitotic index and the percentage of positive for proliferating cell nuclear antigen (PCNA) nuclei of hepatocytes. When turpentine oil was administered in rats 24 h prior to PH, an increase of hepatocyte proliferation, evident from tritiated thymidine incorporation into liver DNA and TK activity was observed, P < 0.001, compared with that found in simply partially hepatectomized ones. The administration of turpentine oil simultaneous with PH did not further affect the proliferation of hepatocytes. This fact suggests that a stimulatory effect of acute phase response induction on hepatocyte proliferation occurs, when the maximum circulation of acute-phase reactants coincides with the time point of PH, enhancing by this way the hepatocyte replicative capacity.