Carnitine contents in remnant liver, kidney, and skeletal muscle after partial hepatectomy in rats: randomized trial

Carnitine, an important carrier of free fatty acid that is transported into mitochondria for beta-oxidation, was thought to be one of the key factors in the regulation of liver regeneration. If the carnitine content is insufficient in the hepatocyte, it might impair the energy substrate's transport and the energy charge required for cell regeneration. The purpose of this study is to evaluate the changes of carnitine content in remnant liver, kidney, and skeletal muscle simultaneously after partial hepatectomy in rats. Partial hepatectomy with resection of the median and left lateral lobes was performed on male Wistar rats. Rats with a sham operation comprised a control group. This study was an experimental randomized trial. Ten rats from each group were sacrificed before the operation and at 6, 24, 48, and 72 hours after the operation. The carnitine content, as total and free forms, in remnant liver, kidney, and skeletal muscle were quantified by high-performance liquid chromatography. The carnitine contents in the remnant liver increased significantly at 6, 24, and 48 hours after partial hepatectomy (p < 0.01). The increase of total carnitine content was more obvious than that of the free form. In contrast, the decreasing concentrations of total carnitine and free carnitine in the kidney were significant (p < 0.01). In skeletal muscle the total carnitine content decreased to a small extent, and it was observed only at 6 hours after partial hepatectomy (p < 0.05). It is suggested that remnant liver promoted the generation of carnitine, whereas kidney and skeletal muscle released their stored carnitine at an early stage after partial hepatectomy. As a result, the influx of the carnitine into hepatocytes increased at the regenerative stage. The carnitine content of remnant liver is sufficient during the early posthepatectomy stage.     

Effects of benfluorex metabolites on membrane fluidity and insulin-related processes

Hepatocyte growth factor (HGF) is a potent mitogen for the maturation of hepatocytes in vitro which plays a role in liver regeneration in vivo. In addition, transforming growth factor-beta 1 (TGF-beta 1) is also a potent regulator of liver regeneration. In attempting to clarify the mechanisms related to liver regeneration after partial hepatectomy, we investigated the expression of HGF and TGF-beta 1 in rats with liver cirrhosis (LC). A rat model of LC was prepared using carbon tetrachloride (CCl4). The expression of HGF mRNA in both the LC and control groups showed a similar time-course with the highest expression seen at 18h after a 70% hepatectomy. The expression of TGF-beta 1 mRNA peaked at 18h after partial hepatectomy in the LC group and at 48h in the control group. The 5-bromo-2'-deoxyuridine (BrdU) labeling index for the LC group at 24, 48, and 72 h after partial hepatectomy was 9.2%, 5.9%, and 1.8%, while for the control group it was 7.0%, 11.7%, and 6.8%, respectively. The BrdU labeling index in the LC group was thus suppressed earlier than that in the control group. We therefore postulate that regeneration of the remnant liver in the presence of LC accelerates immediately after partial hepatectomy, but the extent of regeneration is insufficient because of an early cessation due to an early expression of TGF-beta 1.     

Extracellular matrix remodeling at the early stages of liver regeneration in the rat

Previous studies have shown that activity of urokinase-type plasminogen activator (u-PA) increases very rapidly (within 1 minute) after partial hepatectomy. In view of the well-recognized roles of u-PA as one of the major initiators of the matrix proteolysis cascade and as an activator of plasminogen and hepatocyte growth factor (HGF), we studied matrix degradation in liver shortly after partial hepatectomy. The activation of plasminogen to plasmin following partial hepatectomy was examined by Western blot analysis, and a small increase in plasmin at approximately 15 minutes followed by a large elevation at approximately 3 to 6 hours after partial hepatectomy was detected. In addition, we found that fibrinogen, the major substrate for plasmin, begins to be degraded at approximately 15 to 30 minutes following partial hepatectomy. Using immunohistochemical staining, we detected that the distribution of fibrinogen in normal liver is localized to the perisinusoidal space surrounding the periportal region. A decreased distribution of fibrinogen in the periportal region was found by 15 minutes and continued through 24 hours following partial hepatectomy. In addition, the distribution of fibronectin in normal liver was localized to the perisinusoidal space surrounding the periportal and the pericentral regions. A strikingly decreased distribution of fibronectin in the periportal region was found at 5 minutes after partial hepatectomy. Furthermore, we observed that the protein levels of laminin, entactin, and fibronectin in an extracellular matrix (ECM)-enriched preparation decreased shortly after partial hepatectomy, and were restored later. No changes were observed with either vitronectin or the integrin chain alpha(v). In contrast to the protein levels of the ECM components, the messenger RNA (mRNA) levels of fibronectin, integrin chain beta1, and integrin chain alpha(v) gradually increased over 18 hours and then decreased thereafter. Taken together, these results suggest that rapid reorganization of selected ECM components are important for hepatocyte proliferation at the early stages of liver regeneration.     

Connections between the tendons of the musculus flexor digitorum profundus involving the synovial sheaths in the carpal tunnel

We earlier described a model of fulminant hepatic failure (FHF) in the rat where partial hepatectomy is combined with induction of right liver lobes necrosis. After this procedure, lack of regenerative response in the residual viable liver tissue (omental lobes) was associated with elevated plasma hepatocyte growth factor (HGF) and transforming growth factor beta (TGF-beta1) levels and delayed expression of HGF and c-met mRNA in the remnant liver. Here, we investigated whether syngeneic isolated hepatocytes transplanted in the spleen will prolong survival and facilitate liver regeneration in FHF rats. Inbred male Lewis rats were used. Group I rats (n = 46) received intrasplenic injection of 2 x 10(7) hepatocytes and 2 days later FHF was induced. Group II FHF rats (n = 46) received intrasplenic injection of saline. Rats undergoing partial hepatectomy of 68% (PH; n = 30) and a sham operation (SO; n = 30) served as controls. In 20 FHF rats (10 rats/group), survival time was determined. The remaining 72 FHF rats (36 rats/group) were used for physiologic studies (liver function and regeneration and plasma growth factor levels). In Group I rats survival was longer than that of Group II controls (73 +/- 22 hr vs. 33 +/- 9 hr; P < 0. 01). During the first 36 hr, Group I rats had lower blood ammonia, lactate, total bilirubin, PT, and PTT values, lower activity of liver enzymes, and higher monoethylglycinexylidide (MEGX) production than Group II rats. In Group I rats, livers increased in weight at a rate similar to that seen in PH controls and showed distinct mitotic and DNA synthetic activity (incorporation of bromodeoxyuridine and proliferation cell nuclear antigen expression). Plasma HGF and TGF-beta1 levels in these rats decreased and followed the pattern seen in PH rats; additionally, c-met expression in the remnant liver was accelerated. Hepatocyte transplantation prolonged survival in FHF rats and facilitated liver regeneration. Even though the remnant liver increased in weight four times reaching 30% of the original liver mass, the transplant-bearing rats expired due to inability of the regenerating liver to support the rat.     

Vasopressin modulates liver regeneration in the Brattleboro rat

Liver regeneration following partial hepatectomy is significantly impaired in rats with hereditary vasopressin deficiency (Brattleboro strain), both in rate of DNA synthesis and in return of liver DNA content to normal. Vasopressin treatment at physiological doses ameliorates the defect and thus appears to be an important modulator of liver regeneration in response to partial hepatectomy in the rat.     

Hepatocyte proliferation and gene expression induced by triiodothyronine in vivo and in vitro

Subcutaneous injections of hormone triiodothyronine in rats resulted in peak blood levels at 24 hr with return to baseline by 96 hr. The injections stimulated a liver regeneration response that resembled in timing and in magnitude of DNA synthesis (peak, 24 hr) that induced by 40% hepatic resection. The principal proliferation was of hepatocytes. Although there were some temporal differences from the gene expression of transforming growth factor-alpha, transforming growth factor-beta, and c-Ha-ras that are known to follow partial hepatectomy, the overall profile of these changes was similar to those after partial resection. The effect was liver specific and could be reproduced three times with no diminution in response in the same animal with injections at 10-day intervals. No response was detected in kidney or intestine. This effect in intact animals contrasted with the minimal ability of triiodothyronine to stimulate hepatocytes in culture. However, when the culture medium was enriched with epidermal growth factor, there was a dose-related response to triiodothyronine. The totality of these experiments provides a preliminary basis for the creation with pharmacological techniques of an in vivo hyperplastic hepatic condition permissive of transfection of new genes, as an alternative to partial hepatectomy. Although triiodothyronine was the test agent used, other hepatic growth factors singly or in combination could be candidates for this purpose.