Electroneutral Na-coupled cotransporter expression in the kidney during variations of NaCl and water metabolism

The purpose of the present study was to analyze the long-term regulation of renal bumetanide-sensitive Na+-K+-2Cl- cotransporter and thiazide-sensitive Na+-Cl- cotransporter gene expression during changes in NaCl and water metabolism. Male Wistar rats exposed to high or low NaCl intake, saline loading, dehydration, water loading, and furosemide administration during 7 days were studied. Control groups had access to regular food and tap water. Rats were kept in metabolic cages for 4 days before and during the experiment to determine daily urinary electrolyte excretion and osmolarity. At the end of the experiment, creatinine clearance and serum electrolyte levels were also measured. Kidneys were excised and macroscopically subdivided into cortex and outer and inner medulla. Total RNA was extracted from each individual cortex or outer medulla by use of the guanidine/cesium chloride method. The Na+-K+-2Cl- cotransporter expression in outer medulla total RNA was assessed by nonradioactive Northern blot analysis and the Na+-Cl- cotransporter expression in renal cortex total RNA was assessed by semiquantitative polymerase chain reaction. Experimental maneuvers were adequately tolerated, and all groups developed the appropriate renal response to each challenge. However, the level of expression of both cotransporters did not change in any model, except for a 2.8-fold increase in the Na+-Cl- cotransporter expression during dehydration. We conclude that nephron adaptation to 7-day modifications in NaCl and water metabolism does not include changes in the amount of electroneutral sodium-coupled cotransporter gene expression at the mRNA level.

Role of NO in cyclosporin nephrotoxicity: effects of chronic NO inhibition and NO synthases gene expression

The role of nitric oxide (NO) during cyclosporin renal vasoconstriction was evaluated by glomerular hemodynamic and histological changes produced by chronic NO synthesis inhibition and neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) NO syntheses mRNA expression in renal cortex and medulla. Uninephrectomized rats treated during 7 days with vehicle (Veh), cyclosporin A (CsA) 30 mg/kg, CsA + nitro-L-arginine methyl ester (L-NAME), and Veh + L-NAME (10 mg/dl) in the drinking water were studied. Increase in arterial pressure and afferent and efferent resistances, as well as decrease in glomerular plasma flow, ultrafiltration coefficient, and single-nephron glomerular filtration rate were significantly greater with CsA + L-NAME than with CsA alone. The increase in afferent resistance was higher with CsA + L-NAME than with Veh + L-NAME. In addition, glomerular thrombosis, proximal tubular vacuolization, and arteriolar thickening were more prominent. In renal cortex, eNOS mRNA expression exhibited a 2.7-fold increase in CsA, whereas, in medulla, nNOS and iNOs expression were lower in CsA than in Veh, while eNOS tended to increase. Our results support the hypothesis that NO synthesis is enhanced at cortical level during CsA nephrotoxicity, counterbalancing predominantly preglomerular vasoconstriction. Higher NO production could be the result of increased eNOS mRNA expression.

Expression of dipeptidylaminopeptidase IV/CD26 in peripheral blood lymphocytes of hemophilic subjects

CD26 antigen, a 110 kDa membrane glycoprotein with exopeptidase activity (DAP IV), is an activation marker of T lymphocytes preferentially expressed on CD4+ memory cells and involved in T cell proliferation and IL-2 production after antigenic stimulation. We employed cytochemical and immunocytochemical techniques to study DAP IV/CD26 expression in circulating lymphocytes from 40 hemophilic patients, chronically treated with coagulation factors, in order to verify the possible involvement of this molecule in the immunological alterations of hemophilia. In all the hemophiliacs DAP IV activity was significantly lower than in the controls, independently of the quantity of blood transfused and previous exposure to viruses. This reduction may be responsible for the impaired proliferative response of lymphocytes to antigens and mitogens, notoriously observed in hemophilia. Whereas in the group of HIV- patients CD26 expression was similar to that of normal controls, in the 8 HIV+ hemophilic patients both percentages of positive lymphocytes and intensity of staining were significantly lower. In only 4 of the 8 cases was this deficit associated with CD4+ cell depletion. The significant selective loss of CD26 expression observed in HIV+ patients is probably an early event after HIV infection and seems to occur even before CD4 cell depletion. In conclusion, evaluation of DAP IV/CD26 might be a useful option for monitoring the immunological alterations of all hemophilic patients, HIV positive or not, chronically treated with coagulation factors.

A prospective multicenter study of hepatocellular carcinoma in italian hemophiliacs with chronic hepatitis C. The Study Group of the Association of Italian Hemophilia Centers

To assess the risk factors, natural history, and eligibility for curative treatment of early-detected hepatocellular carcinoma (HCC), 385 hemophiliacs who were treated with blood or plasma derivates for at least 10 years and had persistently elevated aminotransferase values underwent an annual screening with an abdominal ultrasound examination and measurement of the serum alpha-fetoprotein (AFP) level. Of these, 355 had serum antibody to hepatitis C virus (anti-HCV), 29 had anti-HCV and hepatitis B surface antigen (HBsAg), and one had HBsAg alone; 141 had serum antibody to human immunodeficiency virus (anti-HIV). During 48 months of follow-up study, six patients developed HCC. All HCC patients had a HCV-related cirrhosis and had been exposed to HCV risk at a median age of 40 years. All patients had a multicentric tumor, which was not eligible for curative treatment. Univariate analysis showed age, cirrhosis, and baseline AFP levels to be significantly associated with an increased risk of HCC. By multivariate analysis, the risk of HCC was infinite in patients with cirrhosis, 31.0 for those with baseline AFP higher than 11 ng/mL, and 17.9 for those more than 45 years of age. In conclusion, the risk of cancer was greater for patients infected later in life, particularly those with cirrhosis and high AFP. Annual screening of hemophiliacs with ultrasound and AFP fails to identify potentially curable tumors because the diagnosis is made at a late stage of the disease.

Activation of the hemostatic process in patients with unruptured aortic aneurysm before and in the first week after surgical repair

BACKGROUND AND OBJECTIVE

It has been previously suggested that activation of coagulation and fibrinolysis may sometime occur in patients with unruptured aortic aneurysm. However, the incidence of this complication and the effect of surgical repair are unknown. The objective of our study was to gain further information on this topic.

METHODS

We investigated activation of the hemostatic process in 20 consecutive patients with unruptured abdominal aortic aneurysm. We then evaluated the effect of surgical repair of the vascular abnormalities.

RESULTS

Both before and in the first week after surgery, the large majority of patients showed clear signs of activation of coagulation (increased plasma levels of prothrombin fragment 1 + 2 and fibrin peptide A), and many had low levels of the natural anticoagulant antithrombin III. Platelets were activated in all cases (high levels of plasma beta-thromboglobulin), and signs of platelet consumption (thrombocytopenia and/or increased mean platelet volume) were present in most of them.

INTERPRETATION AND CONCLUSIONS

Activation of the hemostatic process occurs in nearly all patients with abdominal aortic aneurysm and could play a role in the hemorrhagic and thrombotic events that can complicate the clinical development of these subjects.

Semi-quantitative PCR: a tool to study low abundance messages in the kidney

Some specific functions are often localized to unique cellular types or structures in organs such as kidney, brain, blood, and endocrine glands. As a result, it is not uncommon that gene products, although heavily expressed in some cell types within these organs, ultimately appear as low abundance products when total RNA is probed, resulting in decreased power of the conventional Northern blot analysis. To study gene expression in these circumstances, more sensitive techniques like RNAse protection assay and quantitative or semi-quantitative PCR strategies have been developed. In the present study, we provide a detailed description of the semi-quantitative PCR strategy in our laboratory. Using specific primers to amplify fragments from the neuronal isoform of the nitric oxide synthase and the thiazide-sensitive Na+:Cl- cotransporter (low abundance messages in the kidney), we show that the semi-quantitative PCR strategy is a valuable tool when low abundance messages are to be studied.

The electroneutral Na(+)-(K+)-Cl- cotransport family

Recently the molecular identification of the major electroneutral sodium-potassium-chloride entry mechanisms present on apical membranes of distal nephron segments of the mammalian kidney, on basolateral membranes of many non-renal epithelial cells and on certain non-epithelial tissues has been achieved. These transporters represent a major pathway for cellular uptake of chloride critical for chloride absorptive and secretory processes and for cell volume regulation following cell shrinkage. In the mammalian kidney, these sodium-coupled chloride cotransporters represent the major target sites for clinically useful diuretics including the "loop" diuretics [furosemide (Lasix) and bumetanide (Bumex)] and thiazides (such as, chlorothiazide, hydrochlorothiazide and metolazone). Although these Na-(K)-Cl cotransporters exhibit functional and pharmacological differences, they clearly evolved from a common ancestral gene and thus form a new gene family. This information is already advancing our understanding of the evolution, structure and function of these transporters both in renal handling of sodium and in hypertension.

Natural history and risk factors for thrombosis in 360 patients with antiphospholipid antibodies: a four-year prospective study from the Italian Registry

PURPOSE

To assess the natural history and risk factors for thrombosis in a large cohort of unselected patients with antiphospholipid antibodies.

PATIENTS AND METHODS

Three hundred sixty consecutive patients (118 males, 242 females, median age 39 years [range 2 to 78]) fulfilling the currently accepted criteria for diagnosis of lupus anticoagulant (LAC) (n = 326) and/or raised immunoglobulin G anticardiolipin antibodies (IgG ACA) (n = 185) were collected from 16 Italian institutions and prospectively observed for a median of 3.9 years (range 0.5 to 5). Main endpoints were the occurrence of arterial or venous thrombosis, the outcome of pregnancies, and any severe complications leading to hospitalization or death.

RESULTS

Thirty-four patients developed a thrombotic complication, with a total incidence of 2.5% patient-years. Multivariate logistic regression analysis identified two independent risk factors for thrombotic events: a previous thrombosis (RR 4.9; 95% CI, 1.76 to 13.7; P < 0.005) and IgG ACA titer above 40 units (RR 3.66; 95% CI, 1.24 to 10.8; P < 0.01). A total of 28 pregnancies were observed in 25 women and 11 (39%) were abortive. Adverse pregnancy outcomes were significantly more frequent in women with a history of miscarriage or vascular occlusion (9/16, 56%) than in asymptomatic women (2/12, 17%) (P = 0.035). Four patients developed non-Hodgkin's lymphoma during the follow-up. Eighteen patients died. Vascular events and hematological malignancies represented the most frequent causes of death (n = 5 for each).

CONCLUSIONS

The present study shows that: (a) previous thrombosis and ACA titer > 40 U are independent predictors of thrombosis; (b) history of miscarriage or vascular disease is significantly associated with adverse pregnancy outcome; (c) hematological malignancies can develop during follow-up in patients with antiphospholipid antibodies.

Thrombin activity and early outcome in unstable angina pectoris

BACKGROUND

The blood coagulation system is frequently activated in the acute phase of unstable angina, but it is unknown whether the augmented function of the hemostatic mechanism may serve as a marker of increased risk for an early unfavorable outcome.

METHODS AND RESULTS

Plasma concentrations and 24-hour urinary excretion of fibrinopeptide A were prospectively determined in 150 patients with unstable angina. All patients underwent 24-hour Holter monitoring, during which time urine was collected; at the end of this period, a blood sample was taken and coronary arteriography was performed. The patients were followed up for the occurrence of cardiac events (death and myocardial infarction) until they underwent coronary revascularization or until they were discharged from the hospital. Fibrinopeptide A plasma levels and 24-hour urinary excretion were found to be abnormally elevated in 50% and 45% of the study population, respectively. During hospitalization, 11 patients developed myocardial infarction and 2 patients died. Kaplan-Meier analysis demonstrated a significantly higher probability of developing cardiac events in patients with abnormal rather than normal plasma levels of fibrinopeptide A (P<.01), whereas no difference in outcome was observed between patients with normal and those with abnormal 24-hour urinary excretion. Cox regression analysis showed that the only variables independently related to an early unfavorable outcome were the presence of persistent ischemia during 24-hour Holter monitoring (P<.0001), the presence of intracoronary thrombosis at angiography (P=.016), and abnormal fibrinopeptide A plasma levels (P=.038).

CONCLUSIONS

Patients with unstable angina pectoris and abnormal fibrinopeptide A plasma levels are at increased risk for an early unfavorable outcome.

Portal and mesenteric thrombosis in protein S (pS) deficiency

Portal and/or mesenteric thrombosis is a rare occurrence, and often an underlying hypercoagulable state can be found. We describe a case in which a mesenteric infarction due to mesenteric venous thrombosis occurred as the first manifestation of an inherited type I deficiency of protein S, whereas signs of portal thrombosis emerged later.

[Molecular structure of luminal diuretic receptors]

Since day to day sodium and water intake is more or less constant, the output by urinary sodium excretion is the key to maintain extracellular fluid volume within physiologic ranges. To achieve this goal, the kidneys ensure that most of the large quantities of filtered sodium are reabsorbed, a function that takes place in the proximal tubule, the loop of Henle and the distal tubule, and then the kidneys adjust the small amount of sodium that is excreted in urine in such a way that sodium balance is maintained. This adjustment occurs in the collecting duct. Three groups of diuretic-sensitive sodium transport mechanisms have been identified in the apical membranes of the distal nephron based on their different sensitivities to diuretics and requirements for chloride and potassium: 1) the sulfamoylbenzoic (or bumetanide)-sensitive Na+:K+:2CI- and Na+:CI- symporters in the thick ascending loop of Henle; 2) the benzothiadiazine (or thiazide)-sensitive Na+:CI- cotransporter in the distal tubule; and 3) the amiloride-sensitive Na+ channel in the collecting tubule. The inhibition of any one of these proteins by diuretics results in increased sodium urinary excretion. Recently, the use of molecular biology techniques, specially the functional expression cloning in Xenopus laevis oocytes, has led to the identification of cDNA's encoding members of the three groups of diuretic-sensitive transport proteins. The present paper reviews the primary structure and some aspects of the relationship between structure and function of these transporters as well as the new protein families emerging from these sequences. It also discusses the future implications of these discoveries on the physiology and pathophysiology of kidney disease and sodium retaining states.