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Biomedical subjects

D R Borges

Publications and source records attributed to D R Borges.

At least 19 recordsLinked to original sources
PubMed2001

Portal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2-type receptors.

BACKGROUND: We have shown that the portal hypertensive response to bradykinin in normal rats is mediated by B2 receptors. METHODS: By using isolated and exsanguinated rat liver perfusion, we studied the portal hypertensive response to bradykinin or des-Arg9-bradykinin (B1 agonist) in inflamed or cirrhotic rat livers. Livers were perfused with bovine serum albumin Krebs-Henseleit buffer (pH 7.4; 37 degrees C) at a constant flow rate, in the absence or presence of des-Arg9[Leu8]-bradykinin or HOE 140 (B1 and B2 receptor antagonists, respectively). Bradykinin (140 nmol) or des-Arg9-bradykinin was injected as a bolus via the afferent route to the liver. RESULTS: Basal perfusion pressure in liver-cirrhotic rats was higher than in normal rats. In normal, inflamed, or liver-cirrhotic rats, the presence of the B1 antagonist did not change the portal hypertensive response to bradykinin, while the B2 antagonist abolished this response. A 140-nmol dose of des-Arg9-bradykinin did not change the perfusion pressure; 700 nmol of this B1 agonist produced an insignificant perfusion pressure increase. The perfusion pressure increase induced by bradykinin in cirrhotic livers was lower than in normal livers. CONCLUSIONS: The portal hypertensive response to bradykinin in inflamed or cirrhotic rat livers is mediated by B2 receptors, but not B1 receptors, and there is a contracting hyporeactivity to bradykinin in cirrhotic rat livers.

Analysis of Variance↗
PubMed2000

Thimet oligopeptidase EC 3.4.24.15 is a major liver kininase.

Bradykinin (BK) is a potent hepato-portal hypertensive agent although it is efficiently inactivated by the liver. The organ converts angiotensin I to AII, but at a much slower rate than it inactivates BK. We had previously identified EC 3.4.24.15 as an hepatic bradykinin inactivating endopeptidase that hydrolyzes BK at the F5-F6 bond. The aim of this study was to determine the relative importance of BIE, as compared to other kininases, in normal, cirrhotic or inflamed rat livers, as well as in samples of human liver. Using specific substrates and inhibitors we showed that: 1) purified BIE preparation hydrolyzed BK and a BK analogue (BK-Q) with similar efficacy; BK-Q was functionally active since it caused an increase in hepato-portal pressure, as did BK itself. 2) BK degradation in rat serum was performed by ACE since BIE and prolylendopeptidase (PEP) activities were negligible. 3) normal rat liver homogenate contained a large amount of BIE activity which was eliminated by a specific EC 3.4.24.15 inhibitor; ACE and PEP activities were negligible. 4) There was no difference (p>0.05) in BIE activity in the liver homogenates from rats with normal, inflamed or cirrhotic livers. 5) BIE activity was efficiently removed from livers (normal, inflamed or cirrhotic) that were perfused with TritonX-100.6) Human liver had an similar enzymatic pattern although ACE activity was detected. We concluded that in normal, inflamed or cirrhotic rat livers, as well as in the human liver, the bradykinin inactivating endopeptidase (EC 3.4.24.15), and not ACE, is the major hepatic kininase.

Amino Acid Sequence↗
PubMed2000

Thrombocytemia as a predictor of portal hypertension in schistosomiasis.

Sufferers of schistosomiasis mansoni can evolve a clinical form of the disease associated with portal hypertension. To differentiate this form, routine clinical tests and biological indices were evaluated. In all, 54 HBsAg- and HCV-negative patients were studied, 42 with schistosomiasis and 12 normal volunteers. Using clinical criteria, ultrasonography, and endoscopy, the schistosomiasis patients were classified into two groups: mild chronic form (MS, N = 14) and chronic form associated with portal hypertension (PH, N = 28). The laboratory parameters of the MS group did not differ from the controls. The PH group differed from the others in prothrombin index, thrombocytemia, gamma-glutamyltransferase, serum alpha2-macroglobulin, and the calculated indices. ROC plot cutoff levels verified that isolated thrombocytemia was the most efficient marker for discrimination of the PH and MS forms. Thrombocytemia of 130 x 10(9) platelets/liter discriminated the groups with an 86% accuracy when all patients were analyzed and 96% when only schistosomiasis patients who did not consume alcohol were included.

Adult↗
PubMed2000

The hepatic clearance of recombinant tissue-type plasminogen activator decreases after an inflammatory stimulus.

We have shown that tissue-type plasminogen activator (tPA) and plasma kallikrein share a common pathway for liver clearance and that the hepatic clearance rate of plasma kallikrein increases during the acute-phase (AP) response. We now report the clearance of tPA from the circulation and by the isolated, exsanguinated and in situ perfused rat liver during the AP response (48-h ex-turpentine treatment). For the sake of comparison, the hepatic clearance of a tissue kallikrein and thrombin was also studied. We verified that, in vivo, the clearance of 125I-tPA from the circulation of turpentine-treated rats (2.2 +/- 0.2 ml/min, N = 7) decreases significantly (P = 0.016) when compared to normal rats (3.2 +/- 0.3 ml/min, N = 6). The AP response does not modify the tissue distribution of administered 125I-tPA and the liver accounts for most of the 125I-tPA (>80%) cleared from the circulation. The clearance rate of tPA by the isolated and perfused liver of turpentine-treated rats (15.5 +/- 1.3 microg/min, N = 4) was slower (P = 0.003) than the clearance rate by the liver of normal rats (22. 5 +/- 0.7 microg/min, N = 10). After the inflammatory stimulus and additional Kupffer cell ablation (GdCl3 treatment), tPA was cleared by the perfused liver at 16.2 +/- 2.4 microg/min (N = 5), suggesting that Kupffer cells have a minor influence on the hepatic tPA clearance during the AP response. In contrast, hepatic clearance rates of thrombin and pancreatic kallikrein were not altered during the AP response. These results contribute to explaining why the thrombolytic efficacy of tPA does not correlate with the dose administered.

Acute-Phase Reaction↗
PubMed1998

Early liver dysfunction in schistosomiasis.

BACKGROUND/AIMS: Liver dysfunction is said to occur only late in the course of schistosomiasis. As albumin levels tend to be normal, the observed prolonged prothrombin time is thought to arise from subclinical consumption coagulopathy. The aim of this study was to further evaluate this matter by studying the role of Schistosoma mansoni and liver function in the genesis of the compromised haemostasis tests in chronic "pure" schistosomiasis patients. METHODS: Twenty-five adults with chronic "pure" schistosomiasis were selected: 12 with the hepatointestinal form (group 2) and 13 with the compensated hepatosplenic form (group 3), as well as 10 matched control individuals (group 1). Alcoholism, viral hepatitis B and C, malnutrition (BMI<20 kg/m2), use of anticoagulant or anti-aggregant drugs and chronic diseases apart from schistosomiasis were carefully excluded. All patients were submitted to abdominal ultrasound and upper digestive endoscopy. Blood samples were used for routine hepatic tests and for transthyretin, prothrombin, antithrombin and protein C antigen determinations by immunodiffusion. Laboratory markers of coagulation activation (prothrombin fragment1+2(F1+2), serine esterases-antithrombin complexes (ATM) and plasminogen activator, tissue type activity (t-PA) were also assayed by ELISA and photometric determination, respectively. RESULTS: Decreased plasma levels of transthyretin (p<0.001), protein C (p:0.006), prothrombin (p:0.022) and antithrombin (p:0.008) contrasted with normal albuminaemia (p:0.094), F1+2 (p:0.061) and ATM (p:0.714) plasma levels in group 3 patients; t-PA activity (p:0.001) on the other hand, were increased in this group. CONCLUSIONS: These results suggest impairment of liver clearance and protein synthesis capacity rather than consumption coagulopathy. They also indicate that changes in liver function are not a late event in the course of schistosomiasis.

Adult↗
PubMed1998

Plasma-kallikrein clearance during liver regeneration after partial hepatectomy in the rat.

AIMS/BACKGROUND: The liver clears circulating plasma-kallikrein through a receptor-mediated endocytosis process: an initial fast phase is followed by a slow exponential phase. METHODS: To determine whether the clearance rate of plasma-kallikrein is affected during liver regeneration, we perfused isolated rat livers with rat plasma-kallikrein (rPK) at 0, 1, 2, 3 and 7 days after partial hepatectomy or sham operation. RESULTS: Liver regeneration was followed by the expression of the proliferating-cell nuclear antigen (PCNA) labeling index. The serum concentration of alpha2-macroglobulin, an acute phase protein in rats, was measured. At day 1, the fast phase of rPK clearance rate increased in hepatectomized rats when compared with day 0 (4.9+/-0.4 and 3.7+/-0.4 mU/g liver min, p<0.05). However, at day 2, the rPK fast phase clearance rate dropped significantly (2.6+/-0.2, p<0.05), when compared with day 1. No difference was found among the sham groups at different days of hepatectomy. These changes seem to be independent of the acute phase reaction. The regenerative liver weight increased continuously during the observation period. PCNA expression increased significantly after hepatectomy, with maximal PCNA-labeling indices at days 1 and 2, declining thereafter. CONCLUSION: The rPK fast phase clearance rate changes during liver regeneration, with a zenith occurring when PCNA labeling index is maximal (day 1) and a nadir occurring at the mitotic phase (day 2).

Animals↗
PubMed1997

Vena cava perfusion in situ: a tool for uptake studies.

While studying the uptake of trypsin and thrombin by the perfused rat liver, we verified that these proteins are internalized neither by hepatocytes nor Kupffer cells. These results raised the possibility that the enzymes might be binding to endothelial cells, either hepatic or vascular. In order to find out if the binding of enzymes to endothelial surface is a liver cell-specific phenomenon, we devised a system to perfuse the rat inferior cava vein in situ. After exsanguination, the vein was perfused with the recirculation of 30 mL of Krebs/BSA solution propellered by a pulsatile flow pump (10 mL/min). The liver was not exsanguinated, but to assure that the organ was indeed excluded from the circuit during the experiment at the end of the perfusion time we added China ink in the perfusion fluid. We verified that trypsin is extracted from the perfusion fluid by the vena cava as efficiently as by the liver, suggesting that the most of the infused trypsin is removed mainly by vascular endothelial cells when the liver perfusion model is used. On the other hand, thrombin is removed mainly by the liver cells since the uptake by the vena cava was insignificant.

Animals↗
PubMed1996

Liver bradykinin-inactivating-endopeptidase is similar to the metalloendopeptidase (EC 3.4.24.15).

The bradykinin-inactivating-endopeptidase (BIE) removal from rat liver, by perfusing the organ with 0.05% Triton X-100, achieved its maximum at 10 min of perfusion and falls to 50% of the maximum in 30 min, a pattern similar to AST removal. Using an internally quenched fluorescent BK analogue (Abz-RPPGFSPFRQ-EDDnp) we further characterized this enzyme: it is activated by low concentrations of 2-mercaptoethanol, inhibited by p-hydroxymercuribenzoate, o-phenanthroline and EDTA, and is resistant to enalapril, E-64 and PMSF. These results suggest that BIE is a metalloendopeptidase containing a thiol group important for its activity. BIE also hydrolyses the peptides Abz-GGFLRRVQ-EDDnp, Abz-GPQGLAGQ-EDDnp, Abz-FRSVQ-EDDnp, and Abz-ARVRRANSFLQ-EDDnp. All these properties are very similar to those described or assayed by us for EC 3.4.24.15, isolated initially from rat testes and then from several organs of different animals. Both BIE and EC 3.4.24.15: hydrolyze the F5S6 bond of the BK fluorescent substrate; are efficiently inhibited by Orlowski specific inhibitor (CFP-AAF-pAB, Ki 4.4 x 10(-7) M and 1.25 x 10(-7) M, respectively); have the same electrophoretic mobility in SDS-PAGE (Mr 78,000); and are both recognized by three polyclonal antibodies raised against rat testes EC 3.4.24.15. In conclusion, BIE appears to be EC 3.4.24.15.

Animals↗
PubMed1996

Clearance of the alpha 2 macroglobulin-trypsin complex and uptake of trypsin by perfused liver.

The uptake and degradation of the alpha 2 macroglobulin-trypsin (alpha 2 m-trypsin) complex have been studied using isolated liver cells but not in the liver as a whole. We report the clearance of the complex by the isolated and exsanguinated liver of Wistar male rats, weighing 150- 280 g, and compare it with that of the free enzyme. The hepatic clearance of the alpha 2m-trypsin complex follows a pattern with a distribution phase followed by an elimination phase, which contrasts with that of trypsin where only the distribution phase is observed. The extraction of trypsin from the perfusate is Ca(2+)-independent (156 +/- 14 pmol/g liver in the presence of 2.5 mM Ca2+, N = 9, versus 140 +/- 8 pmol/g liver in its absence, N = 7) and is not affected by 100 mM NH4Cl (152 +/- 7 pmol/g liver, N = 6), 100 U/ml heparin (164 +/- 14 pmol/g liver, N = 5), 30 microliters/ml carbon particle suspension (150 +/- 13 pmol/g liver, N = 7) or an acute-phase situation induced by turpentine (125 +/- 10 pmol/g liver, N = 6) (P > 0.05, ANOVA). The hepatic clearance of the alpha 2m-trypsin complex is Ca(2+)-dependent (1.8 +/- 0.2 ml/min in the presence of Ca2+, N = 8, versus 0.6 +/- 0.03 ml/min in its absence, N = 4), affected by NH4Cl (< 0.1 ml/min, N = 7), heparin (1.1 +/- 0.2 ml/min, N = 6) and the acute-phase (0.6 +/- 0.1 ml/min, N = 6) but not by the carbon particle suspension (1.8 +/- 0.2 ml/min, N = 7). These results show that trypsin is not internalized by hepatocytes (no NH4Cl effect) or Kupffer cells (no carbon particle effect) and that the alpha 2m-trypsin complex is internalized in a Ca(2+)-dependent process by hepatocytes, but not by Kupffer cells, and is affected by an acute-phase reaction.

Acute-Phase Reaction↗
PubMed1994

Plasma kallikrein clearance by the liver: a review.

1. The liver is the main organ clearing both plasma and tissue kallikreins from the circulation. Hepatocytes are responsible for the internalization of rat plasma kallikrein (RPK) and the clearance of plasma kallikrein by the liver is Ca(2+)-independent. The binding site of RPK to the liver cell is located on its heavy chain which is not exposed on prokallikrein. An S-type lectin accounts for the receptor-mediated endocytosis of RPK. 2. These properties of the liver are affected by pathological situations, particularly the acute-phase response to inflammation, in which the kallikrein-kinin system plays a major role. The hepatic clearance of the alpha 2-macroglobulin-plasma kallikrein complex is less efficient than the clearance of the free enzyme.

Acute-Phase Reaction↗
PubMed1993

Comparison between clearance rates of plasma kallikrein and of plasma kallikrein-alpha-macroglobulin complexes by the liver.

1. alpha-Macroglobulins (alpha Ms) were isolated from the serum of injured rats through a two-stage method: gel filtration and ultracentrifugation. 2. The clearance rates of rat plasma kallikrein (RPK) and alpha Ms-RPK complexes were compared in an isolated rat liver perfusion system: the alpha Ms-RPK complexes are cleared at a much slower rate (half-life ranging from 24 to > 120 min) than does RPK itself (half-life ranging from 13 to 18 min).

Animals↗
PubMed1993

Plasma-kallikrein clearance by the liver of acetaminophen-intoxicated rats.

The liver synthesizes prokallikrein and is the main organ to clear the active enzyme (plasma-kallikrein) from circulation. This clearance, a receptor-mediated endocytosis, is calcium-independent and not affected by the blockade of Kupffer cells. The effects of endothelial cells blockade and of acetaminophen intoxication on the clearance of 10 nM rat plasma-kallikrein (RPK) by the isolated, exsanguinated and perfused rat liver are now reported. Endothelial cells blockade obtained by the addition of large excess (30 uM) of formaldehyde-treated serum albumin to the perfusion fluid does not affect the hepatic clearance of RPK (the half-lives of hepatic uptake were 15.5 +/- 1.0 min in the absence versus 16.5 +/- 1.4 min in the presence of the treated protein, p > 0.05). Some livers were perfused 24 hours after acetaminophen intoxication: 6.6 mmol/kg given i.p. after a 42-hour period of fast. Hepatocyte injury suggested by elevated aminotransferase activity (ALT 10 times control value, AST 30 times control value), acute phase inflammatory response (serum alpha 2-macroglobulin increase) and reduced synthetic function (serum albumin decrease), was confirmed histologically and only zone 3 hepatocytes were necrotic. A 66-hour period of fast does not affect by itself the hepatic clearance of RPK (16.9 +/- 1.3 min of half-life of hepatic uptake) when compared with the control group (15.5 +/- 1.0 min, p > 0.05). On the other hand the RPK clearance by the livers of rats previously intoxicated with acetaminophen was markedly deficient (the half-life of hepatic uptake was 39.2 +/- 3.2 min). These findings suggest that RPK is internalized by hepatocytes, preferentially by those of the perivenular zone of the hepatic acinus.

Acetaminophen↗
PubMed1993

Plasma kallikrein and thrombin are cleared through unrelated hepatic pathways.

Plasma kallikrein (PK) and thrombin (TH), serine proteinases formed from inactive precursors, participate in important body defence mechanisms. The isolated hepatocyte recognizes TH, and the liver clears PK by calcium-independent receptors through mechanisms that are not yet clearly understood. It is known that heparin impairs the binding of TH to isolated liver cells through the inhibition of high affinity receptors. Using an isolated, exsanguinated and perfused rat liver preparation we confirmed that the TH hepatic clearance is calcium-independent and affected by heparin; PK clearance rates both in the presence (t1/2 10 +/- 2 min) or the absence (t1/2 10 +/- 1 min) of heparin were similar; the presence of beta-galactosides does not impair the TH clearance but adversely affects the PK clearance and a large excess of TH does not impair the PK clearance rate (t1/2 6 +/- 1 min). These results indicate that PK and TH are cleared by calcium-independent but otherwise unrelated hepatic pathways and suggest that TH may indeed facilitate the PK clearance by the liver.

Amino Acid Sequence↗
PubMed1993

Ethanol challenge in non-alcoholic patients with schistosomiasis.

AIMS: To evaluate serum gamma glutamyltransferase (GGT) activity in a group of non-alcoholic patients with the hepatointestinal form of schistosomiasis; and the response of both GGT and alkaline phosphatase to an ethanol challenge in two subgroups of patients with different baseline serum concentrations of GGT. METHODS: Seventy six non-alcoholic, non-smoking hepatitis B virus (HBV) negative men with normal body mass index, who denied blood product transfusion or use of medication, were studied (30 healthy volunteers (control group) and 46 patients with the hepatointestinal form of schistosomiasis). GGT activities were determined in all subjects and the ethanol test (measurement of GGT and alkaline phosphatase (ALP) before and 24 hours after the ingestion of 1 g/kg of ethanol) was performed in 14 patients (7 with GGT below 25 IU/l and seven with GGT above 25 IU/l). The ethanol serum concentrations were determined in the samples collected one hour after ingestion of the solution in four patients with schistosomiasis. RESULTS: The mean serum ethanol concentration one hour after the ingestion was 0.7 g/l and all patients were clinically intoxicated. GGT was below 25 IU/l in all 30 volunteers and in 33 of the patients with schistosomiasis. In 13 patients the GGT varied from 28 to 140 IU/l. The two enzymes GGT and ALP determined in the 14 patients submitted to the test were positively correlated in the baseline samples (r = 0.8130) as well as in the samples obtained 24 hours after stimulation (r = 0.7921). Neither the plasma activity of GGT nor the GGT:ALP ratio was affected by the ethanol challenge. CONCLUSIONS: These results suggest that the mechanisms for the increase of GGT serum activity in schistosomiasis and in alcoholism differ. In the latter, microsomal induction increases GGT serum activity, while alterations in the biliary tree may be responsible for the increase observed in patients with schistosomiasis.

Adult↗
PubMed1993

The enteroinsular axis and endocrine pancreatic function in chronic alcohol consumers: evidence for early beta-cell hypofunction.

Chronic alcohol consumers may have, as judged by functional criteria, exocrine as well as endocrine pancreatic dysfunction, the latter represented by a decreased insulin response to an oral glucose load. To investigate whether this decreased insulin response was due to an ethanol-induced beta-cell dysfunction or to an ethanol-induced dysfunction of the enteroinsular axis, we determined glucose, insulin, and C-peptide plasma concentrations following an oral and an intravenous glucose load in 16 healthy volunteer nonalcohol consumers and in 10 chronic alcohol consumers. In each group, total integrated response for glucose did not significantly change whether glucose was given orally or intravenously, indicating isoglycemic glucose loads. The total integrated response values for insulin in the alcoholic group following both glucose loads as well as C-peptide plasma concentrations were significantly lower than in the control group. Moreover, in both groups the insulin TIR values following the oral glucose load were significantly greater than the values obtained following the intravenous glucose load, indicating an incretin effect. These results indicate that the decreased insulin response observed in alcoholics was not caused by a dysfunction of the enteroinsular axis because it also occurred following an intravenous glucose load, but by an ethanol-induced beta-cell dysfunction because C-peptide and insulin were proportionally decreased in this group.

Adult↗
PubMed1992

The recognition site for hepatic clearance of plasma kallikrein is on its heavy chain and is latent on prokallikrein.

We partially purified the glycoproteins prokallikrein and kallikrein from rat plasma. The purification of rat plasma kallikrein may result in two forms: an intact form (alpha, M(r) 84-87 kDa) and a partially degraded form (beta, M(r) 46-51 kDa). The alpha-form is composed of a heavy chain (M(r) 50 kDa) and a light chain (M(r) 34-37 kDa) linked by a disulfide bond. The catalytic site is found on the light chain. The beta-form has a partially degraded heavy chain (M(r) 28 kDa). Using a preparation of exsanguinated and perfused rat liver, we verified that rat plasma prokallikrein is not activated by the liver and that neither the proenzyme nor the light chain is removed by the organ. Both forms (alpha and beta) of the active enzyme are similarly removed from the perfusate. We also observed that the clearance of plasma kallikrein is temperature-dependent, and not affected by substances that inhibit binding to galactosyl-, mannosyl-, fucosyl- or phosphomannosyl-specific lectins, but inhibited by beta-galactosides. We suggest that: (a) the binding site to hepatocytes is latent on prokallikrein and is located on its heavy chain, more specifically on the 28-kDa fragment still present in the beta form of the active enzyme and (b) plasma kallikrein is recognized by an S-type lectin.

Amides↗