The influence of hormones and inflammatory agents on C-reactive protein, cortisol and alanine aminotransferase in the plaice (Pleuronectes platessa L.)

Endotoxin stimulates production of both C-reactive protein (CRP) and cortisol in the plaice within 24 hr. Cortisol alone (optimum dose i.p. 500 micrograms/300 g wt fish) also stimulates CRP production and the possibility that endotoxin acts through cortisol was examined. Dexamethasone suppresses cortisol production but elevates CRP. Cortisol levels are restored to normal within 24 hr of endotoxin injection. Turpentine and ACTH which stimulate cortisol do not affect CRP. Endotoxin and cortisol have no significant effect on alanine aminotransferase activity in the serum and liver although it is elevated in the serum within 24 hr of the administration of adrenalin or turpentine.     

The effects of cortisol on the primary response of mouse spleen cell cultures to heterologous erythrocytes

Cell viability and the production of direct PFC were studied in mouse spleen cell cultures after cortisol treatment in vivo or in vitro at various times relative to primary stimulation with SRBC in vitro.Cortisol treatment in vivo reduced spleen cell numbers by 88% after 48 hr, but cultures of the remaining cells produced as many PFC in vitro as did cultures of equal numbers of normal spleen cells.In normal spleen cell cultures incubated with cortisol for 4 hr prior to the addition of antigen, peak responses of PFC/culture and PFC/10⁶ cells occurred 24 hr later than in controls and averaged, respectively, 27% and 141% of control values. Minimum viable cell numbers were observed in cortisol-treated cultures after 3 days; thereafter cell numbers gradually increased. These results were not significantly altered when cultures were treated simultaneously with cortisol and antigen.The response was not suppressed if the addition of antigen preceded that of cortisol by more than 4 hr. Suppression was also considerably reduced if fetal calf serum was used when preparing cells for culture.     

The effects of adrenal hormones, endotoxin and turpentine on serum components of the plaice (Pleuronectes platessa L.)

1. Within 24 hr of injection into plaice, cortisol, deoxycorticosterone, adrenalin or endotoxin cause an increase (P less than 0.001) in circulating C-reactive protein (CRP). Turpentine and soluble dexamethasone have no effect. 2. The increase in CRP with endotoxin is not enhanced with adrenalin or deoxycorticosterone, and in conjunction with cortisol the increase is additive. 3. Changes in CRP are independent of the amounts of serum amyloid P-component or total protein. 4. Turpentine, cortisol and adrenalin cause a rapid increase in circulating glucose. 5. It is concluded that some adrenal hormones stimulate the CRP acute phase response in plaice, without an apparent provoking agent.     

Effects of intraperitoneal injection of cortisol on non‐specific immune functions of Ctenopharyngodon idella

After grass carps Ctenopharyngodon idellus were injected with cortisol, with (CBC) and without (C) a cocoa butter carrier, the effects of both slowly and rapidly acting exogenous cortisol on their non‐specific immune functions were investigated. On the one hand, after injection with CBC, the cortisol concentration and lysozyme activity in fish serum were enhanced and were sustained at high levels for a long period (30 days). The killing activity in the serum declined with time, and phagocytosis of head kidney macrophages diminished significantly (P < 0·05 or P < 0·01). The leukocrit values in the high dose group (31·8 mg cortisol fish^?1) increased over time, however, with the maximum average being 5·6% at day 30. The spleen mass index in the high dose group was 0·93 × 10^?3 after 30 days, notably lower (P < 0·05) than that in the control group. In addition, a decrease in resistance to Aeromonas hydrophila infection in cortisol‐treated fish was shown, with the final cumulative mortalities being 54·5 and 66·7% in the low and high dose groups, respectively. On the other hand, there was a decrease in both serum cortisol concentration and lysozyme activity of the experimental fish within 2 weeks after injection with C, where plasma bactericidal activities in the high dose group (31·8 mg cortisol fish^?1) were remarkably lower (P < 0·01) than those in the control group at each sampling, but were increased slightly over time. The results of which were different from those in the CBC trial. Phagocytic activity of head kidney macrophages and spleen mass index decreased significantly (P < 0·05), while there were increases in leukocrit value and cumulative mortality due to A. hydrophila. The results of which were similar to those in the CBC trial. This study indicated that the injection of cortisol depressed the non‐specific immune functions of the grass carp and increased its susceptibility to disease.     

Mouse C-reactive protein and endotoxin-induced resistance

Patterson, L. T. (University of Texas, Galveston), and R. D. Higginbotham. Mouse C-reactive protein and endotoxin-induced resistance. J. Bacteriol. 90:1520-1524. 1965.-The relationship between the level of C-reactive protein (CRP) in the sera of mice and resistance to Staphylococcus aureus infection after the injection of Escherichia coli endotoxin was studied. The CRP level was essentially unchanged at 6 hr after endotoxin, and resistance was slightly decreased. At 24 hr after endotoxin, both CRP levels and resistance were increased. Since the increase in the CRP level and resistance appeared to be associated, it was of interest that, when mouse CRP was tested for in vitro reactions with several strains of bacteria, cells of all species of gram-positive bacteria tested (including S. aureus) were agglutinated by CRP. E. coli was not agglutinated under the conditions of the test. It is proposed that mouse CRP is an opsonin, and possibly a lysin, and is involved in nonspecific resistance to infection with S. aureus.     

Contribution of different organs to increased glucose consumption after endotoxin administration

Glucose utilization of different organs (spleen, liver, ileum, kidney, skin, lung, and testis) was investigated in vivo in conscious rats 3, 24, or 48 h after treatment with 100 micrograms of endotoxin/100 g of body weight. Glucose uptake was determined by the 2-deoxyglucose technique, which was validated by demonstrating that endotoxin treatment did not alter either the intracellular retention of the phosphorylated metabolites (P-2-dGlc) of the tracer or the discrimination against 2-deoxyglucose in pathways of glucose metabolism. At 3 h after endotoxin the accumulation of P-2-dGlc was markedly increased in the liver (4.8-fold), spleen and skin (2.9-fold), lung (2.4-fold), and ileum and kidney (2.1-fold), as compared to time-matched controls. This effect was sustained in the liver at 24 and 48 h, was diminishing but still significant in spleen, ileum, and kidney, and absent in skin and lung. Accumulation of P-2-dGlc in the testis remained unchanged after endotoxin. Glucose uptake by individual organs and their contribution to whole body glucose utilization in control and endotoxin-treated rats were compared based on P-2-dGlc accumulation data. Organs rich in mononuclear phagocytes (liver and spleen) exhibited a marked and prolonged increase in glucose uptake after endotoxin. Yet the bulk of the increment in the whole body glucose disappearance rate (Rd) was due to three large tissues (skin, intestine, and muscle, accounting for more than 80% of the total P-2-dGlc accumulation in soft tissues), which showed a more moderate and transient increase in glucose utilization.     

The Effects of Bacterial Endotoxin on the Infection of Mice with Trypanosoma cruzi*

Mice (Rockland strain) infected with Trypanosoma cruzi strain Tulahuén were treated with Escherichia coli endotoxin before, simultaneously with, and after inoculation of the parasites. The peak parasitemias of endotoxin-treated mice were higher than those of nontreated infected animals, regardless of the time of endotoxin administration. Peak parasitemias occurred at the same time in infected nontreated mice as in animals given endotoxin before or simultaneously with the trypanosomes. If endotoxin was administered 24 hr after the infection, a delay in the peak parasitemia was noted. Changes in the survival time were not observed unless endotoxin was given 24 hr postinfection. Infected mice had an increasing susceptibility to the lethal effect of endotoxin. The LD₅₀ of endotoxin decreased from 675 μg for normal mice to 230, 92, and 18 μg for infected animals 1, 3, and 8 days after the infection, respectively. In the infected mice, the endotoxin-detoxifying ability of the spleen was found to be impaired.     

A new fluorescent viability test for fungi cells

Examination of the distribution of radioactivity in rat tissues during the first 24 hr after administration of ochratoxin A-¹⁴C demonstrated maximum accumulation in stomach and kidney. The highest counts were observed in stomach, lung, kidney, thymus, spleen and heart during the first 6 hr after treatment, whereas the brain, liver muscle, duodenum, jejenum, ileum, and cecum exhibited the greatest counts at 18 hr after toxin exposure.The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Metabolie Aspects in Mice Administered Live Salmonella typhimurium

The influence of intraperitoneal inoculation of live Salmonella typhimurium on carbohydrate and lipid metabolisms in mice was investigated at doses of 9.2 × 10⁷ cells, 1.9 × 10⁸ cells, and 3.8 × 10⁸ cells. The hepatic glycogen content in mice at 18 hr after the inoculation decreased in inverse proportion to an increase in the injection dose. The activities of hepatic phosphorylase and G-6-P_ase increased significantly after 2 hr, but after 18 hr the levels of both enzyme activities, especially G-6-P_ase, declined in inverse porportion to an increase in dose of viable cells administered to the mice. The levels of serum glucose and free fatty acids (FFA) in mice markedly decreased at doses of 1.9 × 10⁸ and 3.8 × 10⁸ cells after a transient rise at early stage (1 hr) after the injection. Marked hypertriglyceridemia was seen in infected mice. However, the activity in serum lipoprotein lipase (LPL) was reduced by an increase in the injection dose. The effect of intraperitoneal administration of viable cells on the serum triglyceride level was prevented in mice immunized with S. typhimurium endotoxin or administered with the anti-endotoxin serum. These results indicate that hypertriglyceridemia mainly results from the action of endotoxin in the pathogen. Serum lactate dehydrogenase (LDH) activity markedly increased at the dose of 3.8 × 10⁸ cells within 8–16 hr, and the infected mice exhibited a leakage of isozymes LDH-3 and 5 in the serum 16 hr post-inoculation.     

Vascular effects, formation, clearance and release of endothelin peptides in the pig

The formation, release, clearance and vascular effects of endothelin (ET)-like immunoreactivity (-LI) was studied in the pig in vivo. Intravenous infusion of ET-1, 2 and 3 (20 pmol/kg/min for 20 min) increased vascular resistance in the kidney, spleen and skeletal muscle. The most pronounced effects were evoked by ET-1 which caused increases in renal, splenic and skeletal muscle vascular resistance of 554, 528 and 38%, respectively, and a threshold response was observed at 80 pmol/l ET-LI in arterial plasma. During the infusion a large portion of arterial plasma, ET-LI was cleared over the kidney, spleen and skeletal muscle, whereby the most pronounced clearance was observed for ET-1 (73–93%). The ET-1 precursor Big-ET (1–39) given in a similar dose produced only a slight increase in renal vascular resistance (by 20%) and was cleared only over the kidney and not over the spleen or skeletal muscle. Using an ET-1 specific antiserum it was found that plasma ET-1 levels increased 11-fold during the infusion of Big-ET, indicating formation of ET-1 from Big-ET. The half-lives of circulating ET-1, 2 and 3 were 1.3–2.1 min and of Big-ET 8.9 min. Induction of asphyxia for 2 min increased the overflow of ET-LI from the spleen, suggesting local release, and caused splenic vasoconstriction. During i.v. administration of endotoxin for 4 h, arterial plasma ET-LI increased 7-fold and renal and splenic vasoconstrictor responses developed that correlated significantly with the arterial plasma ET-LI. Furthermore, a local release of ET-LI in the spleen was observed during endotoxin administration. Chromatographic characterization of the ET-LI in plasma during endotoxin administration revealed presence of ET-1 and Big-ET. It is concluded that there exists specificity both concerning the vasoconstrictor effects and removal from the circulation of ET peptides, both mechanisms being most prominent for ET-1 in the kidney. Furthermore ET-1 seems to be formed from circulating Big-ET and release of ET-LI can be detected during situations like asphyxia and sepsis.     

Changes in the activities of enzymes, especially lactate dehydrogenase, in endotoxin-poisoned mice.

Carbohydrate metabolic disorders were investigated by means of enzyme activities in mice (ddYS) injected intraperitoneally with endotoxin from Salmonella typhimurium. The mice exhibited hyperglycemia 2 hr after administration of endotoxin and hypoglycemia at 18 hr. Activity of hepatic phosphorylase in the endotoxin-poisoned mice at 2 hr was slightly higher than that in the control mice, whereas the level of this activity was not significantly different from that in the controls after 18 hr. Glucose-6-phosphatase activity in the poisoned mice increased by 2 hr after injection, but decreased by 18 hr. The blood lactate level in the poisoned mice transiently decreased until 3 hr after injection, but the mice exhibited a marked lactacidemia by 8–24 hr. The time course of lactate dehydrogenase (LDH) activity in various tissues was examined in mice injected with endotoxin. The activity of hepatic LDH declined to about two-thirds of that of the control mice after 16 hr, and was restored to the normal level by 48 hr. LDH in the cardiac muscle was markedly activated (by about 37%) in the early period (3–6 hr) after administration of endotoxin, and this activity gradually declined. However, the activity of LDH in the skeletal muscle showed a tendency similar to the rise and fall of the levels of blood lactate, and was restored to the normal value at 72 hr after injection. On the other hand, the serum LDH activity in the poisoned mice increased about 1.75-fold by 16 hr after injection. Mice injected with endotoxin exhibited a leakage of the isozymes LDH 3 and 5, but the origin of the leakage is uncertain. Similar elevation in the activities of transaminases (GPT and GOT) and malate dehydrogenase was found in the mouse serum at 16 hr after injection of endotoxin.     

POLYMETHACRYLIC ACID: INDUCTION OF LYMPHOCYTOSIS AND TISSUE DISTRIBUTION

Polymethacrylic acid (PMAA) induces up to a three-fold increase in the lymphocyte population of peripheral blood in rats, goats and calves after intravenous administration. Other routes of administration are less effective. A maximum lymphocytosis is achieved after 3 hr with all doses in excess of 30 mg PMAA/kg body weight; over the next few hours the lymphocyte level declines to normal. Granulocytes increase steadily for the first 7 hr before declining. Multiple doses of PMAA 2 hr apart failed to maintain or significantly alter the lymphocytosis. PMAA was labelled with ¹²⁵I and ¹⁴C, and was traced to various sites in the rat. The greatest accumulation of radioactivity was in the spleen, lungs, liver, kidney, adrenals and mesenteric lymph nodes (with ¹⁴C-PMAA). The accumulation appeared more specific for spleen and lymph nodes since there was only a small loss of activity following removal of blood by whole body perfusion. This supports previous findings indicating that these two tissues play a major role in the development of lymphocytosis. Accumulation in the bone marrow may be indicative of stem cell mobilization. The results are discussed in terms of the lymphocytosis-inducing mechanism and the site of action of PMAA and the possible clinical application to ECIB therapy is considered.     

Cortisol metabolism in the domestic cat and implications for non-invasive monitoring of adrenocortical function in endangered felids

Three domestic cats were given i.m. injections of ³H-cortisol to determine the time course and relative proportion of excreted ³H-cortisol metabolites into urine and feces. Most urinary radioactivity was detected in the first sample collected at 3.9 ± 2.5 hr postinjection and accounted for 13.9 ± 2.1% of the total radioactivity recovered. High performance liquid chromatography (HPLC) detected four urinary metabolites, one of which (13.7% urinary radioactivity) eluted with the ³H-cortisol reference tracer and was quantifiable using a commercial cortisol radioimmunoassay (RIA). The majority of cortisol metabolites in feces (85.9 ± 2.1%) was excreted at 22.3 ± 6.2 hr. HPLC analysis detected several fecal metabolites consisting primarily of nonhydolyzable water-soluble forms, none of which eluted with ³H-cortisol or ³H-corticosterone reference tracers. No immunoreactivity was detected in HPLC-separated fecal eluates using the cortisol RIA; however, two of the more polar metabolites were quantifiable using a commerical cortisosterone RIA. The physiological relevance of the immunoreactive fecal metabolites was determined in four domestic cats given an adrenocorticotropin (ACTH) challenge. Increased serum cortisol concentrations were detected within 30 min of ACTH injection, which was maintained for at least 6 hr. A corresponding increase in fecal cortisol metabolite concentrations (ranging from 238% to 826% over individual baseline values) was observed 24–48 hr later. These data indicate that adrenocortical activity can be monitored nonivasively in the cat by measuring cortisol metabolites excreted in feces. This procedure is a potentially valuable tool for endangered felid management to help evaluate responses to physiological and psychological stressors associated with environmental conditions and husbandry practices. (This article is a US Government work and, as such, is in the public domain in the United States of America.) © 1996 Wiley-Liss, Inc.     

Circulating T and B lymphocytes of the mouse. I. Migratory properties

Studies on the identity of thoracic duct lymphocytes (TDL⁴) from normal and T cell-depleted mice indicated that as many circulating B lymphocytes were produced by healthy T cell-depleted mice as normal mice. Proportions of T and B cells from the thoracic duct of CBA mice changed markedly during the first 4 days of drainage from 82% T cells and 16% B cells at 12 hr to approximately equal proportions of both classes after 3 days. In absolute terms, T cells were mobilized rapidly by thoracic duct drainage and B cells very slowly. Histologically, this was reflected in a rapid depletion of the T cell-dependent areas of the lymphoid organs. The B cell-dependent areas, in contrast, became depleted of lymphocytes only after drainage for a week or more.The homing properties of circulating lymphocytes were investigated using TDL from normal and T cell-depleted mice as relatively pure sources of T and B cells, respectively. Four hours after injection of ⁵¹Cr-labeled T and B cells, a large proportion of both cell classes were found in the spleen. By 24 hr, many T cells had left the spleen and appeared in the lymph nodes. Such redistribution by B cells, however, was minimal.Intravenously injected T and B cells, labeled with tritiated uridine (³HU), localized specifically in the T and B cell-dependent areas, respectively, of the lymphoid tissues.³HU-labeled T cells were found to recirculate rapidly from blood to lymph. Labeled B cells, in contrast, recirculated only very slowly.     

Biogenesis of mammalian mitochondria in the renoprival kidney. II. Aspects of mitochondrial DNA synthesis

Mitochondrial DNA (m-DNA) content and factors which might control its concentration were investigated in the renoprival kidney at various times after unilateral nephrectomy. On the basis of mitochondrial protein, m-DNA increased 30% in the renoprival kidney at 24 hr and returned to normal by 48 hr. The total tissue content of m-DNA was also increased at 24 hr. The specific activity of [³H]thymidine incorporated into m-DNA in vivo was decreased markedly at 24 hr after mononephrectomy; at the same time there was a threefold increase of [³H]thymidine incorporation into total cellular DNA. The incorporation into m-DNA was above normal at 48 hr. The mitochondrial specific DNase was decreased 60% at 24 and 36 hr post-mononephrectomy. There was no significant difference in the total radioactivity or total optical density at 260 nm of the acid soluble extract from mitochondria isolated at various times after mononephrectomy. The incorporation of [³H]thymidine into TMP and TDP in the renoprival kidney was not different from normal but there was a decrease in the incorporation into TTP. It is suggested that the increase in mitochondrial DNA could be due to a decrease in the rate of degradation rather than an increase in synthesis.     

Electrolyte changes,cell volume regulation and hormonal influences during acclimation of rainbow trout (Salmo gairdnerii) to salt water

• 1.1. Rainbow trout were acclimated to salt water (1.5, 2.0 or 3.0%, which means 40, 60 or 85% concentrated sea-water) and the electrolyte, glucose and cortisol concentrations of the plasma as well as the extra- and intracellular muscle space, the muscle electrolyte concentrations and the ATPase activity were analysed.
• 2.2. Plasma osmolality, Na⁺, Ca²⁺ and Mg²⁺ concentrations of the plasma had a maximum at 24 hr after the start of acclimation when acclimated to 3.0% salt water. Plasma osmolality, Na⁺ and Mg²⁺ concentrations were significantly higher during the whole acclimation time when exposed to 3.0% salt water.
• 3.3. Variations and regulations of ECS and ICS were clearly demonstrated. The intracellular electrolyte concentrations were also maximal at 24 hr.
• 4.4. The plasma glucose level was just slightly elevated, but the cortisol level clearly indicated a stress response at 24 hr.
• 5.5. The activity of gill Na-K-ATPase increased during the acclimation time.
• 6.6. The regulatory processes in trout during acclimation to salt water are compared with those occurring in tilapia and carp.

     

Increased ratio of serum cortisol to cortisone in acute-phase response

BACKGROUND/OBJECTIVES: 11beta-Hydroxysteroid dehydrogenase (11beta-HSD) enzymes convert cortisol into inactive cortisone and vice versa. While 11beta-HSD type 2 (mainly localized in the kidney) unidirectionally inactivates cortisol to cortisone, type I isoform (mainly localized in the liver) acts bidirectionally and can thus potentially restore cortisone to active cortisol. The aim of this pilot study was to investigate whether the serum cortisol:cortisone ratio is altered during the acute-phase response, possibly due to altered modulation of 11beta-hydroxysteroid dehydrogenase isoforms. METHODS: Using liquid chromatography electrospray tandem mass spectrometry, cortisol and cortisone were measured in the serum of hospitalized patients with normal and abnormal CRP concentrations, the latter indicating acute-phase response. Fifteen unselected samples were analyzed, all with a CRP concentration within one of the following ranges to cover a wide range of CRP concentrations evenly: <5, 5-20, 21-50, 51-100, 101-200, and >200 mg/l. RESULTS: In the heterogeneous study population, increased CRP concentrations significantly correlated with an increased cortisol:cortisone ratio (p < 0.001; r = 0.65, Spearman correlation coefficient). This correlation was independent of increased serum cortisol concentrations found by multivariate regression analysis. The median ratio was 6.4 (interquartile range 5.5-7.4; n = 30) in patients with a CRP concentration < or =20 mg/l, and 11.2 (interquartile range 8.8-13.9; n = 60) in patients with CRP >20 mg/l (p < 0.01). CONCLUSION: The balance between serum cortisol and cortisone is altered during acute-phase response with a shift towards active cortisol, suggesting that 11beta-HSD isoenzymes play a role in the modulation of systemically available cortisol during acute illness.     

Effect of turpentine oil on C-reactive protein (CRP) production in rainbow trout (Oncorhynchus mykiss)

The effect of turpentine oil on C-reactive protein (CRP) production was studied in rainbow trout (Oncorhynchus mykiss). Serum CRP concentration was estimated by sandwich enzyme-linked immunosorbent assay using anti-rainbow trout CRP monoclonal antibody (mAb) AC4 and polyclonal antibody. Intracellular CRP was demonstrated by flow cytometry using anti-trout CRP mAb. Hepatocytes, head kidney macrophages, spleen lymphocytes and peripheral blood lymphocytes showed reaction against AC4, but RTG-2 fibroblastic line cells, derived from rainbow trout gonad did not. This is the first report on the detection of intracellular CRP in fish. CRP levels decreased significantly 1 day after intramuscular injection of turpentine oil and remained low for 14 days. Significant decreases in the expression of CRP in hepatocytes, head kidney macrophages and spleen lymphocytes after injection of turpentine oil were found. The reduction of serum CRP concentration after turpentine oil injection may be attributed to decreases in intracellular CRP synthesis.     

Parathyroid hormone-related protein is induced during lethal endotoxemia and contributes to endotoxin-induced mortality in rodents.

BACKGROUND: Parathyroid hormone-related protein (PTHrP) is a ubiquitous and highly conserved vasoactive peptide whose role and regulation in normal physiology remain an enigma. Recently, we demonstrated that low-dose endotoxin (LPS) induces intrasplenic, but not systemic, levels of PTHrP; and that tumor necrosis factor, a pro-inflammatory cytokine, is the major mediator of this effect. We have therefore hypothesized that, with higher, lethal doses of endotoxin, PTHrP could be induced in multiple tissues to such a degree that it could contribute to the lethality of septic shock. MATERIALS AND METHODS: Northern blot analysis was used to measure PTHrP mRNA levels in vital organs of rats after administration of a near lethal dose (5 mg/250 g) of LPS (or vehicle alone). Plasma levels of PTHrP were also measured by immunoradiometric assay. The ability of the immunoglobulin fraction of two different PTHrP(1-34) antisera to protect from LPS-induced lethality was also studied in mice using survival analysis. RESULTS: In response to a near-lethal dose of endotoxin, PTHrP mRNA levels increased acutely in every vital organ examined (spleen, lung, heart, kidney, and liver). Circulating levels of PTHrP also increased, peaking 2 hr after administration of high-dose endotoxin. Passive immunization of mice with anti-PTHrP(1-34) antibody 6 hr prior to administration of a lethal dose of LPS protected mice from endotoxin-induced death (p < 0.00005). CONCLUSIONS: These results suggest that PTHrP belongs to the cascade of pro-inflammatory cytokines induced during lethal endotoxemia that is responsible for the toxic effects of LPS.     

Tissue distribution and clearance of soluble murine TNF receptors in mice

In this study, clearance of sTNFR was investigated. The data show that bilateral nephrectomy results in an increase of the levels of both sTNFR after which a new steady state situation develops, suggesting that other organs, apart from the kidneys, are involved in clearing of sTNFR. Bilateral nephrectomy also leads to an increase in circulating TNF. This TNF was detected by ELISA and appeared to be not biologically active. To investigate whether the endotoxin induced increase in sTNFR is dependent of renal function, endotoxin was injected in nephrectomized mice. The data show that nephrectomy followed by endotoxin injection resulted in a further increase of the levels of both sTNFR. However, the endotoxin induced increase in nephrectomized mice was similar to the situation in normal mice after LPS indicating that the endtoxin induced increase is kidney independent in these mice. To investigate the relative participation of various organs in sTNFR clearance, ¹²⁵I labelled sTNFR-P75 was injected. The data reveal that the majority of the sTNFR is removed from the circulation by the kidneys although indications for involvement of the liver and the lungs were also obtained. Calculation of the parametric clearance revealed that nephrectomy resulted in a 50% reduction of sTNFR-P75 clearance. Furthermore, the data presented strongly suggest that sTNFR release seems to be a continuous process, which is in balance with clearance of the sTNFR by the kidney, although other organs such as the liver and the lungs are involved.