Dephosphorylation of endotoxin by alkaline phosphatase in vivo.

Natural substrates for alkaline phosphatase (AP) are at present not identified despite extensive investigations. Difficulties in imagining a possible physiological function involve its extremely high pH optimum for the usual exogenous substrates and its localization as an ecto-enzyme. As endotoxin is a substance that contains phosphate groups and is usually present in the extracellular space, we studied whether AP is able to dephosphorylate this bacterial product at physiological pH levels. We tested this in intestinal cryostat sections using histochemical methods with endotoxin from Escherichia coli and Salmonella minnesota R595 as substrate. Results show that dephosphorylation of both preparations occurs at pH 7.5 by AP activity. As phosphate residues in the lipid A moiety determine the toxicity of the molecule, we examined the effect of the AP inhibitor levamisole in vivo using a septicemia model in the rat. The results show that inhibition of endogenous AP by levamisole significantly reduces survival of rats intraperitoneally injected with E. coli bacteria, whereas this drug does not influence survival of rats receiving a sublethal dose of the gram-positive bacteria Staphylococcus aureus. In view of the endotoxin-dephosphorylating properties of AP demonstrated in vitro, we propose a crucial role for this enzyme in host defense. The effects of levamisole during gram-negative bacterial infections and the localization of AP as an ecto-enzyme in most organs as well as the induction of enzyme activity during inflammatory reactions and cholestasis is in accordance with such a protective role.

A physiologic function for alkaline phosphatase: endotoxin detoxification.

Alkaline phosphatase (AP), a common enzyme present in many species including humans, has been studied extensively. Although the enzyme is routinely applied as a marker for liver function, its biologic relevance is poorly understood. The reason for this is obvious: the pH optimum of AP in vitro, as measured with the usual test substrates (+/-10.5), greatly exceeds the physiologic pH range as it occurs in biologic tissues. We now hypothesize that this relatively high pH optimum in vitro is related to dissociation of acidic groups in the protein preparation, which leads to the formation of negatively charged groups in the vicinity of the active site of the enzyme. These negatively charged groups may promote the activity of AP. We examined the possibility that endotoxin is a natural substrate for this enzyme because this phosphorylated substance is able to supply multiple negatively charged residues in the microenvironment of the enzyme at a physiologic pH level. Phosphate groups in the endotoxin molecule are known to be essential for the biologic activities of this bacterial product. The present study demonstrates that in intestinal and renal tissue specimens in vitro, AP is endowed with endotoxin dephosphorylating activity at pH levels closer to the physiologic range. This is also illustrated by our experiments in vivo showing that the toxicity of endotoxin is significantly reduced after exposure to AP preparations, as tested by inducing a local intradermal inflammatory reaction in rats. Collectively, our data suggest that the ubiquitous enzyme AP may accomplish protection against endotoxin, an equally ubiquitous product of Gram-negative bacteria that may cause lethal complications after an infection with these micro organisms.

In vitro complement-dependent binding and in vivo kinetics of pneumococcal polysaccharide TI-2 antigens in the rat spleen marginal zone and follicle.

For a better understanding of the spleen-dependent induction of the humoral immune response against thymus-independent type 2 antigens, we have studied the in vitro and in vivo localization of different capsular pneumococcal polysaccharides (PPSs) in the rat spleen. In this study, we found that in vitro binding of PPS types 3, 4, 6B, 9N/V, 14, and 23F was dependent on complement (probably a C3 fragment) and that the localization was predominantly restricted to the marginal-zone B lymphocytes and the follicular dendritic cells. In vivo, we observed with increase of time a shift of localized antigens. Shortly after injection, all PPS types localized in the marginal-zone B lymphocytes, then localized in the outer follicular mantle, and finally were found to be diffuse in the complete follicle and follicle corona. PPS types 3 and 9N/V and later also PPS type 23F localized additionally in red pulp macrophages. In particular, the localization in the marginal zone is important since the low flow in this area in combination with strongly CD21+ B cells, which are activated early, gives a maximum opportunity for the induction of a primary humoral immune response with subsequent differentiation into plasma cells or migration to the germinal center. In addition, the localization of PPSs at follicular dendritic cells should be considered important in the induction of an ongoing immune response not restricted to the spleen.

Human immune response to pneumococcal polysaccharides: complement-mediated localization preferentially on CD21-positive splenic marginal zone B cells and follicular dendritic cells.

A functionally intact spleen with a marginal zone, containing B cells with high density of surface C3d-receptors (CD21), is essential for the ability to induce a primary immune response to thymus-independent type 2 (TI-2) antigens. Main representatives of natural TI-2 antigens are capsular pneumococcal polysaccharides (PPSs). In this study the localization of different types of PPS antigen is determined in human spleen tissue. Our findings indicate that a main type of TI-2 antigen, PPS, localizes preferentially in the marginal zone. PPSs show co-localization with C3, presumably C3d, at the surface of strongly CD21+ B cells equipped for rapid activation. This enables a rapid primary humoral response. The other main PPS localization at follicular dendritic cells in germinal centers, relevant for isotype switching of anti-PPS antibodies, does not seem to be dependent on the presence of specific immunoglobulin. This may explain the finding of specific IgG in an early stage after antigenic challenge. It seems likely that complement C3 fragments (likely C3d), bound to PPSs, enable PPS localization at B-cell and follicular dendritic cell surfaces by binding to CD21, the C3d receptor.

Increased epithelial cell proliferation in the colon of patients with acromegaly.

To gain insight into the possible physiological mechanisms responsible for the increased incidence of colonic neoplasms in patients with acromegaly, a prospective cohort study was carried out in 30 patients with acromegaly, a prospective cohort study was carried out in 30 patients with acromegaly. Seven patients had newly diagnosed acromegaly and 23 were studied during follow-up. Serum growth hormone and insulin-like growth factor-1 (IGF-1) were determined on two separate occasions. During diagnostic endoscopy, mucosal biopsies were obtained for immunohistochemical determination of sigmoidal epithelial cell proliferation, expressed as labeling index (LI). Duodenal and fecal bile acid analyses were performed using gas-liquid chromatography. Results were compared with normal ranges of the laboratory. An increased overall LI was found in 54% of the patients. Increased LI of the luminal, middle, and basal crypt compartments was found in 11, 64, and 28%, respectively. Similarly, comparisons of the mean +/- SEM of the overall LI and the LI of the middle and basal compartments between acromegalic patients and a control group showed overall LI 10.0 +/- 0.8% versus 5.7 +/- 0.6% (P < 0.001), middle LI 12.1 +/- 1.2% versus 5.0 +/- 0.6% (P < 0.001), and basal LI 17.1 +/- 1.3% versus 10.8 +/- 1.3% (P < 0.01). Duodenal and fecal bile acid proportions were within the normal ranges of the laboratory. There was a positive correlation between growth hormone and overall LI (r = 0.55, P < 0.01) by least square regression analysis. There was no correlation between duodenal bile acid composition and hormone levels. The proportion of secondary bile acids in feces correlated with growth hormone (r = 0.55, P < 0.05) as well as with IGF-1 (r = 0.59, P < 0.05). With multiple regression analyses, only a relation between overall LI and IGF-1 (P = 0.007) remained to hold true. Increased epithelial cell proliferation, most probably due to a direct stimulatory effect of especially IGF-1, contributes to the increased risk of colonic neoplasms in acromegaly.

Histochemical and electron microscopic characterization of hepatic macrophage subfractions isolated from normal and liposomal muramyl dipeptide treated rats.

Subfractions of the hepatic macrophage population, differing in cell size, were isolated from normal rats and rats treated with liposomal muramyl dipeptide (lipMDP) and analyzed histochemically and by ultrastructural peroxidase cytochemistry. The majority of cells in all subfractions of control rats displayed the ultrastructural endogenous peroxidase pattern of resident liver macrophages and showed positive staining with the general macrophage markers nonspecific esterase (NSE) and monoclonal antibody ED1. Heterogeneity in intensity of NSE and ED1 staining was observed among macrophages of different size. Generally, the intensity of NSE and ED1 staining decreased with decreasing cell size. After injection of lipMDP, we observed the appearance of a discrete subpopulation of cells in the liver in addition to the resident macrophages. These cells, containing a nucleus with a characteristic shape, were predominantly recovered in the small-sized fractions and were characterized by an immature ultrastructural macrophage morphology (no or only a few lysosomes and phagosomes) and a lack of ED1 reactivity, NSE, and endogenous peroxidase. We suggest an important role for these cells in lipMDP induced antitumor capacity of the liver.

Randomized, double-blinded, placebo-controlled intervention study with supplemental calcium in families with hereditary nonpolyposis colorectal cancer.

BACKGROUND: A high-fat diet has been recognized for some time as a major risk factor for colorectal cancer. It is thought that fat promotes this disease by increasing the levels of fatty and bile acids within the colon. These acids irritate and damage the epithelial cells of the colon. As a result of this cellular destruction, an increase in the rate of cellular proliferation occurs. Oral calcium supplementation has been proposed as a dietary intervention for individuals at high risk of colorectal cancer because of its ability to reduce rectal epithelial cell proliferation through the binding of fatty and bile acids. Placebo-controlled studies, however, have yielded varying results. PURPOSE: We conducted a randomized, double-blinded, placebo-controlled trial to test oral calcium supplementation in patients at high risk of developing hereditary nonpolyposis colorectal cancer. METHODS: Thirty subjects at risk for this cancer, with an increased epithelial cell proliferation along the colon and rectum, were randomly assigned to either a placebo group (n = 15) or a treatment group (n = 15). They received either oral calcium carbonate (CaCO3) supplements (1.5 g) or placebo (cellulose and starch) three times a day during a 12-week period. Colonic biopsy specimens (rectal, sigmoidal, and descending) were obtained prior to and after the intervention trial, during endoscopy, for determination of labeling index (LI) of whole crypts and crypt compartments by 5-bromo-2'-deoxyuridine incorporation and immunohistochemistry. Proportional bile acid compositions in duodenal bile and cytolytic activity of fecal water were also determined. All P values represent two-tailed tests of statistical significance. RESULTS: Statistically significant reductions, comparing before with after intervention, in rectal whole-crypt LI after receiving either calcium supplements (from 10.9% +/- 5.2% [mean +/- SD] to 6.2% +/- 1.5%; P < .02) or placebo (from 11.7% +/- 4.7% to 8.2% +/- 3.1%; P < .05) were observed. In the three bowel segments, no statistically significant differences were observed between the supplemental calcium and placebo groups. A statistically significant reduction in cytolytic activity was determined during calcium supplementation (from 57% +/- 41% to 32% +/- 30%; P < .05), whereas in the placebo group, it did not change (from 42% +/- 41% to 36% +/- 27%; P > .10). CONCLUSIONS: Oral calcium supplementation was shown to cause only a minor nonstatistically significant reduction of epithelial cell proliferation in the rectum, compared with placebo, and to have no effect on the same parameter in the sigmoid and descending colon in first-degree relatives of hereditary nonpolyposis colorectal cancer patients. IMPLICATION: These results cast doubt on the value of calcium supplementation in the prevention of colorectal cancer, especially in individuals already consuming an adequate amount of dietary calcium.

Immunohistochemical study of hepatic fibrosis induced in rats by multiple galactosamine injections.

Multiple injections of D-galactosamine induce liver fibrosis and cirrhosis in rats. The purpose of this immunopathological study was to correlate inflammation and hepatic extracellular matrix remodeling after repeated administration of galactosamine. Rats were given 10, 20, 30, 40, 60, 80, 100 and 140 intraperitoneal injections of D-galactosamine (500 mg/kg body wt, three times weekly). Controls received injections of saline solution. Cryostat sections of liver tissue obtained on biopsy or autopsy were immunostained with a panel of monoclonal and polyclonal monospecific antibodies reactive with macrophages, T and B lymphocytes, desmin, the extracellular matrix components fibronectin; laminin; collagen types I, III and IV; and the fibronectin receptor alpha 5 beta 1. Total RNA was extracted and Northern-blot analysis was performed with a specific cDNA probe for rat collagen type III. Spotty liver cell necrosis and mild portal and parenchymal inflammation was seen after 10 injections of galactosamine. After 20 to 40 injections, expansion of protal tracts, prominent bile ductular proliferation and gradual formation of fibrous septa were encountered with the development of cirrhosis at later intervals. These progressive histological changes were paralleled by a gradual increase of desmin-positive cells in developing septa with deposition of fibronectin; collagen types I, III, and IV; and laminin. Northern-blot analysis showed that this accumulation of extracellular matrix was not accompanied by increase of mRNA for collagen type III. In conclusion, repetitive administration of galactosamine causes progressive liver disease with prominent bile ductule proliferation and development of fibrous septa. These pathological alterations bear some resemblance to the morphological changes in chronic biliary disease in human beings.

A modified cerium-based histochemical method for detection of experimentally-induced ATPase impairment in glomeruli of the rat kidney.

We studied glomerular ATPase activity, as detectable at the light microscopic (LM) level in cryostat sections of the rat kidney, after unilateral local X-irradiation. The biochemically detectable reduction in glomerular ATPase activity after X-irradiation could be demonstrated at the LM level by application of a modified cerium-based technique. Results show a clear reduction of reaction product in glomeruli in X-irradiated kidneys as compared with the contralateral control kidney. Technical parameters (i.e., tissue fixation, second thickness, cerium concentration of the incubation mixture, and percentage H2O2 added for the amplification step) were established for optimal reproducibility of the staining results. We show that this modified staining protocol allows detection of differences of ATPase activity in contrast to conventional histochemical methods. Inhibition studies with various phosphatase inhibitors and competitive substrate inhibition experiments revealed that the enzyme is specific for nucleoside di- and triphosphatases. Since reduced glomerular adenine nucleotidase activity has recently been recognized as an early event in (experimental) glomerulonephritis, we feel that the new staining protocol presented here may be highly relevant for routine tissue section screening in nephropathological research.

Epithelial cell proliferation in the sigmoid colon of patients with adenomatous polyps increases during oral calcium supplementation.

To study the effect of oral supplemental calcium on colonic epithelial proliferation, 17 adenomatous polyp patients received 1.5 g Ca2+ as calcium carbonate daily during 12 weeks, while on a calcium constant diet, based on the patients' habitual diet. Seven subsequently continued calcium supplementation for 9 months without dietary restrictions. Epithelial proliferation rate in colonic biopsies, expressed as labelling index (%), was determined with 5-bromodeoxyuridine and immunohistochemistry. Biopsies were taken from the midsigmoid at time of polyp excision and at the end of the intervention period. Median labelling index increased from 6.1% before to 8.7% after 12 weeks calcium (n = 17, P < 0.02). This was due to increased labelling in the basal third of the crypts (11.9 vs 16%), whereas labelling in mid and luminal compartments was not affected. Labelling index remained increased after 1 year calcium supplementation at 8.8%. Crypt length was not affected by calcium. These results are in contrast to those of others, who have shown a decrease of rectal epithelial proliferation during similar doses of calcium. Therefore, the effect of nutritional intervention on colonic epithelial proliferation should be studied in biopsies taken not only from the rectum, but also from more proximal parts of the colon. Caution with respect to large scale intervention studies with calcium in high risk groups is mandatory.

Attenuation of anti-Thy1 glomerulonephritis in the rat by anti-inflammatory platelet-inhibiting agents.

Although both ecto-ADPase and prostacyclin (PGI2) inhibit platelets and neutrophils, their action in acute glomerulonephritis is unknown. We tested the PGI2 analog Iloprost and 2chloroadenosine (2Cl-ADO), an analog of adenosine, the end product of nucleotidase activities, during anti-Thy1 nephritis. Rats received anti-Thy1 immunoglobulin G (5 mg/kg body weight, intravenously) and subsequently one subcutaneous injection of either 2Cl-ADO (10 mg/kg body weight; (n = 6) or Iloprost (1 mg/kg body weight; n = 6). Control rats received anti-Thy1 immunoglobulin G with saline (n = 6) or saline alone (n = 6). After 24 hours, kidneys were processed for light-microscopical evaluation. Proteinuria was studied in additional rats. Results showed that both drugs inhibited intraglomerular platelet activation (P < 0.005). 2Cl-ADO also reduced intraglomerular O2- production of neutrophils (P < 0.05), in contrast to Iloprost. Intraglomerular immunoglobulin G deposition, complement activation, neutrophil influx, and myeloperoxidase release were not affected by 2Cl-ADO or Iloprost. However, proteinuria was completely prevented by both drugs. It is concluded that PGI2 and nucleotidases are potentially able to attenuate this form of nephritis by inhibiting platelet activity, whereas nucleotidases also inhibit neutrophil activity in vivo.

Heterogeneity of rat liver and spleen macrophages in gadolinium chloride-induced elimination and repopulation.

Blockade of phagocytosis and selective elimination of macrophages (m phi s) are generally accepted procedures for gaining knowledge about the function of m phi s in vivo. This study demonstrates that intravenous injection of gadolinium chloride (GdCl3) not only blocks phagocytosis by rat liver m phi s (Kupffer cells) but also selectively eliminates the large m phi s situated in the periportal zone of the liver acinus. Repopulation of m phi s starts at 4 days after injection. During repopulation, m phi s are less vulnerable to GdCl3. When repopulation is complete, the new m phi s show the same vulnerability as the original ones. Splenic m phi s are less vulnerable to GdCl3 because only some of the red pulp m phi s transiently disappear. The white pulp m phi s are not affected. Repopulation occurs sooner than in liver. These results indicate that administration of GdCl3 is a suitable approach to studying the in vivo function of large Kupffer cells.

Changes in rectal epithelial cell proliferation and intestinal bile acids after subtotal colectomy in familial adenomatous polyposis.

Subtotal colectomy and ileorectal anastomosis in familial adenomatous polyposis patients can induce temporary regression of adenomas in the rectum. The mechanism for this phenomenon is unclear. We evaluated the effect of colectomy on rectal mucosal proliferation, in relation to changes in bile acid metabolism. Four familial adenomatous polyposis patients were studied before and 3-6 months after surgery, and eight others 7-22 years postoperatively. Within 6 months after surgery, the size of the proliferative zone of the colonic crypts was found to be reduced (P less than 0.05). The proliferative activity of total colonic crypts was not affected within this period. More than 7 years postoperatively, increased cell proliferation of total crypts (P less than 0.02), as well as mid (P less than 0.05) and basal (P less than 0.05) crypt compartments, were observed compared to shortly after colectomy. In duodenal bile, deoxycholic acid was absent shortly after operation, whereas several years after operation only a small fraction (2%) was present. Fecal secondary bile acid excretion diminished after colectomy and did not change several years postoperatively. In postoperative stools only, small proportions of ursocholic and ursodeoxycholic acids (about 5% each) were consistently found. As subtotal colectomy causes a temporary decrease in the length of the proliferative zone of rectal crypts toward a normal pattern, this may explain regression of rectal polyps. This temporary effect may be mediated, at least in part, by decreased amounts of cytotoxic secondary bile acids in the rectal lumen.

Modulation of anti-Thy1 nephritis in the rat by adenine nucleotides. Evidence for an anti-inflammatory role for nucleotidases.

Extracellular adenine nucleotides are considered mediators of inflammation because they modulate functions of neutrophils and platelets. Until now, this role for adenine nucleotides has not been studied in vivo. In particular in the rat kidney, where ATP- and ADPase activity is present in the glomerular basement membrane, studies about the role of nucleotides may increase our understanding of the dynamics of glomerulonephritis (GN). Therefore, we examined effects of adenine derivatives ATP gamma S, ADP beta S and 2chloro-adenosine (2chloro-ADO) in vitro and during anti-Thy1 GN. The in vitro results show that ADP beta S and ATP gamma S are not degraded by glomerular nucleotidases but, on the other hand do stimulate O2- production of peritoneal exudate cells (PEC). In contrast, 2chloro-ADO significantly inhibits O2- production of peritoneal exudate cells. For in vivo studies rats were rendered nephritic by intravenous injection of monoclonal anti-Thy1 IgG (5 mg/kg body weight). Subsequently, rats were treated with saline (group 1, N = 10), 2chloro-ADO (group 2, N = 10), ADP beta S (group 3, N = 10) or ATP gamma S (group 4, N = 10). All analogs (10 mg/kg body weight) were administered both at t = 0 and t = 12 hour. After 24 hours, rats were sacrificed and kidneys were examined histochemically. In an additional group of nephritic rats (N = 5) proteinuria was studied after 2-chloro-ADO treatment. Results show increased intraglomerular platelet aggregation in nephritic rats treated with ADP beta S, whereas 2chloro-ADO inhibits aggregation significantly as compared with nephritic rats receiving saline. The percentage of granulocytes producing O2- is significantly increased in glomeruli after treatment of nephritic rats with ATP gamma S, whereas cell influx itself is not changed. In contrast, 2chloro-ADO inhibits intraglomerular O2- production, which is associated with the complete inhibition of proteinuria in the early phase of anti-Thy1 GN. These data demonstrate significant pro-inflammatory activities of extracellular adenine nucleotides during anti-Thy1 GN suggesting an anti-inflammatory role for glomerular ATP/ADPase, which in concert with 5' nucleotidase converts ATP and ADP to antiinflammatory ADO.

Immunohistochemical study of extracellular matrix in acute galactosamine hepatitis in rats.

A single injection of D-galactosamine hydrochloride induces acute self-limiting liver disease in rats that morphologically resembles drug-induced hepatitis in human beings. In this immunohistochemical study we examined the localization and expression of the hepatic extracellular matrix components fibronectin, laminin, collagen type I, collagen type III and collagen type IV and of the cell surface receptors (integrins) for fibronectin and laminin. Sections of liver tissue obtained at intervals of 6, 12, 18, 24, 30, 36, 48 and 72 hr and 7 and 21 days after galactosamine administration were immunostained with a panel of polyclonal monospecific antibodies and studied independently by two of us. Fibronectin was the first extracellular matrix component found to be increased, 12 hr after galactosamine injection, followed by collagen type III, and, in a later phase, collagen type IV, type I and laminin. Increased deposition of extracellular matrix was found in areas with liver cell necrosis and along sinusoids. Extracellular matrix immunoreactivity reached a maximum at 36 to 48 hr and decreased thereafter to preinjury levels 3 wk after galactosamine. Immunostaining for the fibronectin and laminin receptors revealed tissue localization identical to that of their ligands. However, the intensity of staining was opposite of that for the extracellular matrix, with a decrease of immunoreactivity after 24 to 48 hr. The observed sequence of changes in hepatic extracellular matrix proteins after galactosamine injection resembles the repair reaction in other tissues and may reflect the particular function that each carries out during the process of liver healing after toxic injury.

Bile secretion of sulfated glycolithocholic acid is required for its cholestatic action in rats.

To test our hypothesis that the cholestatic action of sulfated glycolithocholic acid (SGLC) in the rat is related to its interaction with calcium in the biliary tree [R. van der Meer, R. J. Vonk, and F. Kuipers. Am. J. Physiol. 254 (Gastrointest. Liver Physiol. 17): G644-G649, 1988], we have now compared its effects on bile formation in control Wistar rats and mutant Groningen Yellow (GY) Wistar rats. Intravenous injection of 0.6 mumol/100 g body wt of [14C]SGLC in unanesthetized rats with permanent biliary drainage did not induce cholestasis in either of the strains; however, its biliary secretion was strongly impaired in GY rats (12% dose at 1 h after injection vs. 95% dose in controls). Injection of 6.0 and 12.0 mumol/100 g body wt of [14C]SGLC caused an almost complete cessation of bile flow in control rats within 3 and 1 h, respectively. In contrast, administration of the same doses did not cause cholestasis in GY rats. Cholestasis in control rats was preceded by coprecipitation of [14C]SGLC and calcium in bile and incomplete biliary recovery of radioactivity. The hepatic content 15 min after injection of [14C]SGLC (6.0 mumol/100 g body wt) was similar in control and GY rats, 51 and 49% of the dose, respectively. Administration of glycolithocholic acid, the unsulfated parent compound of SGLC (6.0 mumol/100 g body wt), induced a rapid but reversible cessation of bile flow in both controls and GY rats; in this case no precipitation was observed in bile. This study shows that rapid bile secretion of SGLC is required for the induction of cholestasis.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunopathology of alkaline phosphatase-induced granulomatous hepatitis in rats.

Granulomatous inflammation is a specific type of chronic inflammation in which macrophages and T-cell-mediated immunity to the inciting agent play a pivotal role. In the present study, granulomatous hepatitis was induced in rats by the administration of a single intravenous dose of porcine intestinal alkaline phosphatase. The cellular composition of the hepatic granulomas was analyzed in-situ with a number of recently developed mouse anti-rat monoclonal antibodies to cells of the monocyte-macrophage lineage and lymphocyte subsets. Well-developed granulomas consisted of aggregates of macrophages with central modification into epithelioid cells, a peripheral rim of T- and B-lymphoid cells, including considerable numbers of immunoblasts and plasma cells. In addition, the periphery of the granulomas contained many fat storing cells, a sinusoidal cell type thought to play a central role in hepatic fibrosis. Moreover, intense immunostaining for the extracellular matrix proteins fibronectin and collagen type III was observed at the periphery of the lesions. The granulomas persisted for long periods without eliciting liver cirrhosis. Alkaline phosphatase induced hepatic granulomas in the rat may help to elucidate the contribution of cells of the B-lineage to chronic granulomatous inflammation.

Formaldehyde treated albumin contains monomeric and polymeric forms that are differently cleared by endothelial and Kupffer cells of the liver: evidence for scavenger receptor heterogeneity.

Formaldehyde treated albumin (F-HSA) was found to consist of a monomeric and a polymeric fraction. Both fractions were primarily endocytosed by rat liver sinusoidal cells. However, immunohistochemical staining of endocytosed material showed that the relative contribution of the endothelial and Kupffer cells in uptake of the monomer and the polymer differed significantly, with the monomer mainly having an endothelial cell- and the polymer predominantly having a Kupffer cell pattern of distribution. To directly confirm these heterogeneous patterns, we injected in vivo the 125I-labeled F-HSA fractions and isolated the endothelial and Kupffer cells by centrifugal elutriation. 73.7% of the monomeric F-HSA was found in endothelial cells and only 14.9% was found in Kupffer cells. In contrast, the polymeric F-HSA (1500 kD) was mainly endocytosed by Kupffer cells (71%), whereas the endothelial cells contributed only for 24% in hepatic uptake. In vivo studies and isolated perfused rat liver experiments showed that endocytosis of both monomer and polymer was inhibited by co-administration of polyinosinic acid, a well known inhibitor for scavenger receptors, indicating that these receptors on endothelial and Kupffer cells are mainly involved in this uptake process.