Ww Bakker

A NEW ANIMAL-MODEL FOR HUMAN PREECLAMPSIA - ULTRA-LOW-DOSE ENDOTOXIN INFUSION IN PREGNANT RATS

OBJECTIVE An animal model for preeclampsia was developed by means of an ultra-low-dose endotoxin infusion protocol in conscious pregnant rats. STUDY DESIGN Rats received a permanent jugular vein cannula on day 0 of pregnancy, through which endotoxin (1.0 micrograms/kg body weight) (n = 10) or saline solution (n = 6) was infused during 1 hour on day 14 of pregnancy. Blood pressure, albuminuria, and platelet counts were measured, and histopathologic studies was performed in these rats. RESULTS A significant increase of blood pressure (p < 0.05) and of urinary albumin excretion (p < 0.05) was observed in endotoxin-treated pregnant animals, in contrast to control pregnant rats receiving saline solution. Platelet coagulopathy was found and glomerular fibrinogen deposits could be detected only in the endotoxin-treated pregnant rats. In addition, the activity of the glomerular antithrombotic enzyme adenosine diphosphatase was decreased in endotoxin-treated pregnant rats compared with saline solution-treated pregnant rats. CONCLUSION Because histopathologic and clinical events in this model mimic predominant features of human preeclampsia, this model may enable further study into the pathophysiologic mechanisms of this complication of pregnancy.

EXPERIMENTAL GLOMERULONEPHRITIS IN RAT INDUCED BY ANTIBODIES DIRECTED AGAINST TUBULAR ANTIGENS .3. INVITRO EVALUATION OF CELL-MEDIATED IMMUNE-RESPONSES AGAINST IMMUNE-COMPLEXES INFLUENCED BY IMMUNOSUPPRESSIVE THERAPY

In this paper, cell-mediated immunity (CMI) as evaluated by in vitro migration inhibition assays an in vivo delayed type skin reactions in experimental immune complex glomerulonephritis (ECGN) was studied as well as the effect of treatment with immunosuppressive drugs on these immune responses. In glomerulonephritic rats MIF production as well as delayed type skin reactions could be demonstrated directed against tubular brushborder antigen (Fx1A) containing immune complexes or to their constituents (FX1A or rabbit IgG). Treatment of the animals with immunosuppressive drugs during settled disease state (autologous phase) abolished these cellular immune reactions. However, neither the glomerular depositions of rat IgG associated with the autologous phase, nor the urinary excretion was influenced. When treatment of the animals was started simultaneously with the induction of the ECGN both cellular and humoral immune responses as well as proteinuria were affected. It was concluded that although in this glomerulonephritis model specific MIF response after specific stimulation in vitro as well as DTH reactions could be detected against immune complexes or their constituents, these immune reactions seem not to play important role in this ECGN in particular with respect to the proteinuria.

Acute glomerulonephritis after intravenous injection of monoclonal anti-thymocyte antibodies in the rat

Female Wistar rats were injected with (mouse) monoclonal antibodies (Moabs) of different IgG subclasses directed to rat thymocytes or rat tumor cells. Following intravenous injection of antithymocyte Moabs, glomerular binding of mouse IgG was observed during the first 4 days along the GBM and in the mesangium. No staining for mouse IgG was detected in anti-tumor Moab injected rats. Animals injected with IgG 2a anti-thymocyte Moab developed glomerulonephritis and a massive proteinuria in contrast to rats injected with IgG 1 Moab which is non-complement fixing. The glomerulonephritis lesion consisted of microaneurysms and focal and segmental proliferation. Deposits of complement and fibrin could be detected exclusively in rats injected with IgG 2a anti-thymocyte Moab during the whole observation period of 14 days. This is the first demonstration of overt glomerulonephritis lesions on the injection of monoclonal antibodies.

Effect of estradiol and progesterone on the low-dose endotoxin-induced glomerular inflammatory response of the female rat

PROBLEM: Is the endotoxin‐induced glomerular inflammatory response of the female rat under ovarian control?

DO CIRCULATING FACTORS PLAY A ROLE IN THE PATHOGENESIS OF MINIMAL CHANGE NEPHROTIC SYNDROME

This review examines the studies which have been undertaken to test the hypothesis that minimal change nephrotic syndrome of childhood (MCNS) is a primary immune disorder and that there is altered T-cell function which results in release of a circulating factor. This factor alters glomerular permeability, perhaps by modifying charge sites in the glomerular capillary bed, and results in selective proteinuria. The abnormalities in immune function observed in MCNS are summarized, as are the studies of circulating factors which have been identified. Although some agents have been shown to alter capillary permeability, the unequivocal demonstration of such a factor causing selective proteinuria in vivo, either directly or indirectly, is lacking. The question is raised whether intrarenal release or activation of mediators of altered permeability, rather than the systemic release of such factors, may be important in the pathogenesis of MCNS.

Survey of the occurrence of adenosine polyphosphatase in extracellular matrix of rat tissues

SummaryThe extracellular presence of adenosine polyphosphatase was investigated in a number of rat tissues. The enzyme was demonstrated in basement membranes of epithelial cells of duodenum, urinary bladder, tongue, choroid plexus, submandibular salivary gland, lung and kidney, as well as in basement membranes of capillaries in these tissues. Furthermore adenosine polyphosphatase was demonstrated on collagen fibrils and in the cytoplasm of fibroblasts of all investigated tissues. It appears that the presence of adenosine polyphosphatase in basement membranes is a widespread phenomenon. Since extracellular ADP and ATP are known to promote respectively platelet aggregation and inflammation, the presence of extracellular ADP and ATP-hydrolyzing activity might contribute to inhibit these processes.

The Glomerular Polyanion (GPA) of the Rat Kidney

Rat peritoneal exudate cells (PEC) or human peripheral blood cells stimulated with mitogens in vitro were cultured in tissue culture chambers mounted on rat or human cryostat kidney sections. After 20 h, the cultures were discontinued and the glomerular polyanion (GPA) of the glomeruli was studied using the colloidal iron stain. The results show that in contrast to PHA-stimulated cells, rat PEC or human blood cells stimulated with Con-A are able to reduce GPA stainability. It was further shown that rat PEC activated with Con-A for 20 or 48 h were able to suppress in vitro lymphocyte transformation of syngeneic blood lymphocytes in a co-culture system following mitogenic stimulation. In view of recent concepts according to which disturbance of T cell function is associated with in vivo loss of GPA in some forms of the nephrotic state, we conclude that investigation into the possible in vivo significance of the present observations is worthwhile.

LYMPHOKINES IN SENSITIZED RATS .1. MIGRATION-INHIBITORY FACTOR(S) FROM SPECIFICALLY STIMULATED THYMOCYTES INVITRO

Cell-mediated immune responses were studied in Wistar rats by migration inhibition factor (MIF) assays in vitro of lymphoid cells derived from thymus, spleen and peripheral blood and peritoneal exudates and by delayed cutaneous hypersensitivity reactions in vivo. Using PPD and purified diphtheria toxoid as soluble test antigens it appeared that significant migration inhibition was observed only when sensitized thymus and peritoneal exudate cells were used in the direct capillary migration system. Indirect MIF assays, using both capillary and agarose techniques, showed that migration inhibitory activity was found in thymus culture supernatants as well as in spleen culture supernatants of sensitized animals. The MIF activity in thymic cell culture supernatants seemed to be antigen-independent, although in this respect no definitive conclusions can be drawn from the present results. Migration inhibition in direct and indirect techniques always correlated with a positive delayed-type skin reaction. It is suggested that a population of thymus cells of sensitized animals is able to produce MIF on specific antigenic stimulation in vitro. This might support the idea that a cell population within the thymus possesses characteristics of peripheral T cells.

Superoxide–Mediated Glomerulopathy in the Endotoxin–Treated Pregnant Rat

In the present study the role of superoxide in the glomerular damage in the low–dose endotoxin–infused pregnant rats was investigated. On day 14 of pregnancy, 12 rats were infused for 1 h with 1.0 μg/kg bw endotoxin via a permanent jugular vein cannula. Of these rats, 6 were treated with SOD both prior to endotoxin infusion (7,000 U/kg) and 30 min (7,000 U/kg) and 4 h (14,000 U/kg) after the start of the infusion (SOD rats). The other 6 rats received no SOD treatment (endotoxin rats). Control pregnant rats were infused for 1 h with saline (saline rats; n = 6). Urinary albumin was measured on days 15 and 19 of pregnancy. On day 21, rats were sacrificed and kidney specimens were snap–frozen. Cryostat kidney sections were stained for fibrinogen, ecto–ATP diphosphohydrolase (e–ATPase) activity, polymorphonuclear cells, monocytes and various adhesion molecules on the endothelium and the leukocytes. SOD treatment appeared to significantly prevent the increased urinary albumin excretion and the decrease of glomerular e–ATPase activity which were observed in endotoxin–treated rats. This effect of SOD treatment after endotoxin infusion was associated with a significant inhibition of glomerular monocyte influx and a significant inhibition of adhesion molecule expression (glomerular ICAM–1 and VCAM–1 and leukocyte LFA–1 and VLA–4).The present data suggest that in the endotoxin–infused pregnant rat, production of superoxide in the first few hours after the infusion plays a role in the induction of glomerular damage, leading to albuminuria and diminished e–ATPase expression during the following days.

The specificity of nephritogenic antibodies. IV: Binding of monoclonal antithymocyte antibodies to rat kidney

Polyclonal rabbit antirat thymocyte serum (ATS) has been shown to form in situ glomerular immune aggregates following perfusion into normal rat kidney ex vivo. This may be due to the presence of T-cell-like epitopes in the rat kidney, or it may be a result of contaminating anti-connective-tissue antibodies in ATS. To exclude the latter possibility we investigated binding to the rat kidney of three different (mouse) monoclonal antirat thymocyte antibodies (anti-T-cell MoAbs), directed to Thy 1.1 antigen, as well as (control) anti-B-cell MoAbs. The MoAbs were incubated in vitro with kidney sections or perfused into the blood-free rat kidney ex vivo. It was shown using immunofluorescence (IF) and immunoelectron microscopy (IEM) (peroxidase technique) that the anti-T-cell MoAbs used, in contrast to anti-B-cell MoAbs, are able to bind with glomerular capillary walls, and with mesangial structures after incubation in vitro or perfusion ex vivo. Although staining patterns are not completely identical, the reaction product is clearly demonstrated throughout the glomerular basement membrane (GBM) and along the plasma membranes of endothelial and epithelial cells, after contact with either of the three anti-T-cell MoAbs used. It is concluded that the presence of T-cell-like epitopes in the rat kidney may lead to immune complex formation following contact with anti-T-cell MoAbs. The nephritogenicity of rabbit ATS, as well as of some batches of clinically used ATS, may also be explained by this mechanism rather than by the usually assumed presence of contaminating antibodies in these polyclonal antisera.