Nimesulide, a cyclooxygenase-2 preferential inhibitor, impairs renal function in the newborn rabbit.

Tocolysis with nonsteroidal anti-inflammatory drugs (NSAIDs) has been widely accepted for several years. Recently, the use of the cyclooxygenase-2 (COX2) preferential NSAID nimesulide has been proposed. However, data reporting neonatal acute renal failure or irreversible end-stage renal failure after maternal ingestion of nimesulide question the safety of this drug for the fetus and the neonate. Therefore, this study was designed to define the renal effects of nimesulide in newborn rabbits. Experiments were performed in 28 newborn rabbits. Renal function and hemodynamic parameters were measured using inulin and para-aminohippuric acid clearances as markers of GFR and renal blood flow, respectively. After a control period, nimesulide 2, 20, or 200 microg/kg was given as an i.v. bolus, followed by a 0.05, 0.5, or 5 microg.kg(-1).min(-1) infusion. Nimesulide administration induced a significant dose-dependent increase in renal vascular resistance (29, 37, and 92%, respectively), with a concomitant decrease in diuresis (-5, -23, and -44%), GFR (-12, -23, and -47%), and renal blood flow (-23, -23, and -48%). These results are in contrast with recent reports claiming that selective COX2 inhibition could be safer for the kidney than nonselective NSAIDs. These experiments confirm that prostaglandins, by maintaining renal vasodilation, play a key role in the delicate balance regulating neonatal GFR. We conclude that COX2-selective/preferential inhibitors thus should be prescribed with the same caution as nonselective NSAIDs during pregnancy and in the neonatal period.

Circadian regulation of renal function.

Urinary excretion of water and all major electrolytes exhibit robust circadian oscillations. The 24-h periodicity has been well documented for several important determinants of urine formation, including renal blood flow, glomerular filtration, tubular reabsorption, and tubular secretion. Disturbance of the renal circadian rhythms is increasingly recognized as a risk factor for hypertension, polyuria, and other diseases and may contribute to renal fibrosis. The origin of these rhythms has been attributed to the reactive response of the kidney to circadian changes in volume and/or in the composition of extracellular fluids that are entrained by rest/activity and feeding/fasting cycles. However, numerous studies have shown that most of the renal excretory rhythms persist for long periods of time, even in the absence of periodic environmental cues. These observations led to the hypothesis of the existence of a self-sustained mechanism, enabling the kidney to anticipate various predictable circadian challenges to homeostasis. The molecular basis of this mechanism remained unknown until the recent discovery of the mammalian circadian clock made of a system of autoregulatory transcriptional/translational feedback loops, which have been found in all tissues studied, including the kidney. Here, we present a review of the growing evidence showing the involvement of the molecular clock in the generation of renal excretory rhythms.

Chronic bradykinin receptor blockade modulates neonatal renal function.

Recent data indicate that bradykinin participates in the regulation of neonatal glomerular function and also acts as a growth regulator during renal development. The aim of the present study was to investigate the involvement of bradykinin in the maturation of renal function. Bradykinin beta2-receptors of newborn rabbits were inhibited for 4 days by Hoe 140. The animals were treated with 300 microg/kg s.c. Hoe 140 (group Hoe, n = 8) or 0.9% NaCl (group control, n = 8) twice daily. Clearance studies were performed in anesthetized rabbits at the age of 8-9 days. Bradykinin receptor blockade did not impair kidney growth, as demonstrated by similar kidney weights in the two groups, nor did it influence blood pressure. Renal blood flow was higher, while renal vascular resistance and filtration fraction were lower in Hoe 140-treated rabbits. No difference in glomerular filtration rate was observed. The unexpectedly higher renal perfusion observed in group Hoe cannot be explained by the blockade of the known vasodilator and trophic effect of bradykinin. Our results indicate that in intact kallikrein-kinin system is necessary for the normal functional development of the kidney.

Red blood cell microparticles: clinical relevance.

Microparticles are small phospholipid vesicles of less than 1 µm released into the blood flow by various types of cells such as endothelial, platelet, white or red blood cells. They are involved in many biological and physiological processes including hemostasis. In addition, an elevated number of microparticles in the blood is observed in various pathological situations. In the context of transfusion, erythrocyte-derived microparticles are found in red blood cell concentrates. Their role is not elucidated, and they are considered as a type of storage lesion. The purpose of this review is to present recent data showing that erythrocyte-derived microparticles most likely play a role in transfusion medicine and could cause transfusion complications.

Coronary vasomotor control in obesity and morbid obesity: contrasting flow responses with endocannabinoids, leptin, and inflammation.

OBJECTIVES: This study sought to investigate abnormalities in coronary circulatory function in 2 different disease entities of obese (OB) and morbidly obese (MOB) individuals and to evaluate whether these would differ in severity with different profiles of endocannabinoids, leptin, and C-reactive protein (CRP) plasma levels. BACKGROUND: There is increasing evidence that altered plasma levels of endocannabinoids, leptin, and CRP may affect coronary circulatory function in OB and MOB. METHODS: Myocardial blood flow (MBF) responses to cold pressor test from rest and during pharmacologically induced hyperemia were measured with N-13 ammonia positron emission tomography/computed tomography. Study participants (n = 111) were divided into 4 groups based on their body mass index (BMI) (kg/m(2)): 1) control group (BMI: 20 to 24.9, n = 30); 2) overweight group (BMI: 25 to 29.9, n = 31), 3) OB group (BMI: 30 to 39.9, n = 25); and 4) MOB group (BMI ≥40, n = 25). RESULTS: The cold pressor test-induced change in endothelium-related MBF response (ΔMBF) progressively declined in overweight and OB groups when compared with the control group [median: 0.19 (interquartile range [IQR] 0.08, 0.27) and 0.11 (0.03, 0.17) vs. 0.27 (0.23, 0.38) ml/g/min; p ≤ 0.01, respectively], whereas it did not differ significantly between OB and MOB groups [median: 0.11 (IQR: 0.03, 0.17) and 0.09 (-0.01, 0.19) ml/g/min; p = 0.93]. Compared with control subjects, hyperemic MBF subjects comparably declined in the overweight, OB, and MOB groups [median: 2.40 (IQR 1.92, 2.63) vs. 1.94 (1.65, 2.30), 2.05 (1.67, 2.38), and 2.14 (1.78, 2.76) ml/g/min; p ≤ 0.05, respectively]. In OB individuals, ΔMBF was inversely correlated with increase in endocannabinoid anandamide (r = -0.45, p = 0.044), but not with leptin (r = -0.02, p = 0.946) or with CRP (r = -0.33, p = 0.168). Conversely, there was a significant and positive correlation among ΔMBF and elevated leptin (r = 0.43, p = 0.031) and CRP (r = 0.55, p = 0.006), respectively, in MOB individuals that was not observed for endocannabinoid anandamide (r = 0.07, p = 0.740). CONCLUSIONS: Contrasting associations of altered coronary endothelial function with increases in endocannabinoid anandamide, leptin, and CRP plasma levels identify and characterize OB and MOB as different disease entities affecting coronary circulatory function.

Hemodynamic, renal, and endocrine effects of 4-h infusions of human atrial natriuretic peptide in normal volunteers.

A synthetic human atrial natriuretic peptide of 26 aminoacids [human (3-28)ANP or hANP] was infused into normal male volunteers. Six subjects were infused for 4 h at 1-wk intervals with either hANP at the rate of 0.5 or 1.0 microgram/min or its vehicle in a single-blind randomized order. Human (3-28)ANP at the dose of 0.5 microgram/min raised immunoreactive plasma ANP levels from 104 +/- 17 to 221 +/- 24 pg/ml (mean +/- SEM), but it induced no significant change in blood pressure, heart rate, effective renal plasma flow, glomerular filtration rate, or renal electrolyte excretion. At the rate of 1.0 microgram/min, human (3-28)ANP increased immunoreactive plasma ANP levels from 89 +/- 12 to 454 +/- 30 pg/ml. It reduced effective renal plasma flow from 523 +/- 40 to 453 +/- 38 ml/min (P less than 0.05 vs. vehicle), but left glomerular filtration rate unchanged. Natriuresis rose from 207 +/- 52 to 501 +/- 69 mumol/min (P less than 0.05 vs. vehicle) and urinary magnesium excretion from 3.6 +/- 0.5 to 5.6 +/- 0.5 mumol/min (P less than 0.01 vs. vehicle). The excretion rate of the other electrolytes, blood pressure, and heart rate were not significantly modified. At both doses, human (3-28)ANP tended to suppress the activity of the renin-angiotensin-aldosterone system. In 3 additional volunteers, the skin blood flow response to human (3-28)ANP, infused for 4 h at the rate of 1.0 microgram/min, was studied by means of a laser-doppler flowmeter. The skin blood flow rose during the first 2 h of peptide administration, then fell progressively to values below baseline. After the infusion was discontinued, it remained depressed for more than 2 h. Thus, in normal volunteers, human (3-28)ANP at the dose of 1.0 microgram/min produced results similar to those obtained previously with rat (3-28)ANP. It enhanced natriuresis without changing the glomerular filtration rate while effective renal plasma flow fell. It also induced a transient vasodilation of the skin vascular bed.

Structural alterations of the coronary arterial wall are associated with myocardial flow heterogeneity in type 2 diabetes mellitus.

PURPOSE: To determine the relationship between carotid intima-media thickness (IMT), coronary artery calcification (CAC), and myocardial blood flow (MBF) at rest and during vasomotor stress in type 2 diabetes mellitus (DM). METHODS: In 68 individuals, carotid IMT was measured using high-resolution vascular ultrasound, while the presence of CAC was determined with electron beam tomography (EBT). Global and regional MBF was determined in milliliters per gram per minute with (13)N-ammonia and positron emission tomography (PET) at rest, during cold pressor testing (CPT), and during adenosine (ADO) stimulation. RESULTS: There was neither a relationship between carotid IMT and CAC (r = 0.10, p = 0.32) nor between carotid IMT and coronary circulatory function in response to CPT and during ADO (r = -0.18, p = 0.25 and r = 0.10, p = 0.54, respectively). In 33 individuals, EBT detected CAC with a mean Agatston-derived calcium score of 44 +/- 18. There was a significant difference in regional MBFs between territories with and without CAC at rest and during ADO-stimulated hyperemia (0.69 +/- 0.24 vs. 0.74 +/- 0.23 and 1.82 +/- 0.50 vs. 1.95 +/- 0.51 ml/g/min; p < or = 0.05, respectively) and also during CPT in DM but less pronounced (0.81 +/- 0.24 vs. 0.83 +/- 0.23 ml/g/min; p = ns). The increase in CAC was paralleled with a progressive regional decrease in resting as well as in CPT- and ADO-related MBFs (r = -0.36, p < or = 0.014; r = -0.46, p < or = 0.007; and r = -0.33, p < or = 0.041, respectively). CONCLUSIONS: The absence of any correlation between carotid IMT and coronary circulatory function in type 2 DM suggests different features and stages of early atherosclerosis in the peripheral and coronary circulation. PET-measured MBF heterogeneity at rest and during vasomotor stress may reflect downstream fluid dynamic effects of coronary artery disease (CAD)-related early structural alterations of the arterial wall.

Phase-sensitive black-blood coronary vessel wall imaging.

Black-blood MR coronary vessel wall imaging may become a powerful tool for the quantitative and noninvasive assessment of atherosclerosis and positive arterial remodeling. Although dual-inversion recovery is currently the gold standard, optimal lumen-to-vessel wall contrast is sometimes difficult to obtain, and the time window available for imaging is limited due to competing requirements between blood signal nulling time and period of minimal myocardial motion. Further, atherosclerosis is a spatially heterogeneous disease, and imaging at multiple anatomic levels of the coronary circulation is mandatory. However, this requirement of enhanced volumetric coverage comes at the expense of scanning time. Phase-sensitive inversion recovery has shown to be very valuable for enhancing tissue-tissue contrast and for making inversion recovery imaging less sensitive to tissue signal nulling time. This work enables multislice black-blood coronary vessel wall imaging in a single breath hold by extending phase-sensitive inversion recovery to phase-sensitive dual-inversion recovery, by combining it with spiral imaging and yet relaxing constraints related to blood signal nulling time and period of minimal myocardial motion.

Telomere length dynamics in human lymphocyte subpopulations measured by flow cytometry.

To measure the average length of telomere repeats at chromosome ends in individual cells we developed a flow cytometry method using fluorescence in situ hybridization (flow FISH) with labeled peptide nucleic acid (PNA) probes. Results of flow FISH measurements correlated with results of conventional telomere length measurements by Southern blot analysis (R = 0.9). Consistent differences in telomere length in CD8+ T-cell subsets were identified. Naive and memory CD4+ T lymphocytes in normal adults differed by around 2.5 kb in telomere length, in agreement with known replicative shortening of telomeres in lymphocytes in vivo. T-cell clones grown in vitro showed stabilization of telomere length after an initial decline and rare clones capable of growing beyond 100 population doublings showed variable telomere length. These results show that flow FISH can be used to measure specific nucleotide repeat sequences in single cells and indicate that the very large replicative potential of lymphocytes is only indirectly related to telomere length.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

Renal effects of adenosine A1-receptor blockade with 8-cyclopentyl-1,3-dipropylxanthine in hypoxemic newborn rabbits.

The key role of intrarenal adenosine in mediating the hypoxemic acute renal insufficiency in newborn rabbits has been well demonstrated using the nonspecific adenosine antagonist theophylline. The present study was designed to define the role of adenosine A1 receptors during systemic hypoxemia by using the specific A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). Renal function parameters were assessed in 31 anesthetized and mechanically ventilated newborn rabbits. In normoxia, DPCPX infusion induced a significant increase in diuresis (+44%) and GFR (+19%), despite a significant decrease in renal blood flow (RBF) (-22%) and an increase in renal vascular resistance (RVR) (+37%). In hypoxemic conditions, diuresis (-19%), GFR (-26%), and RBF (-35%) were decreased, whereas RVR increased (+33%). DPCPX administration hindered the hypoxemia-induced decrease in GFR and diuresis. However, RBF was still significantly decreased (-27%), whereas RVR increased (+22%). In all groups, the filtration fraction increased significantly. The overall results support the hypothesis that, in physiologic conditions, intrarenal adenosine plays a key role in regulating glomerular filtration in the neonatal period through preferential A1-mediated afferent vasoconstriction. During a hypoxemic stress, the A1-specific antagonist DPCPX only partially prevented the hypoxemia-induced changes, as illustrated by the elevated RVR and drop in RBF. These findings imply that the contribution of intrarenal adenosine to the acute adverse effects of hypoxemia might not be solely mediated via the A1 receptor.

The effects of arterial flow on platelet activation, thrombus growth, and stabilization.

Injury of an arterial vessel wall acutely triggers a multifaceted process of thrombus formation, which is dictated by the high-shear flow conditions in the artery. In this overview, we describe how the classical concept of arterial thrombus formation and vascular occlusion, driven by platelet activation and fibrin formation, can be extended and fine-tuned. This has become possible because of recent insight into the mechanisms of: (i) platelet-vessel wall and platelet-platelet communication, (ii) autocrine platelet activation, and (iii) platelet-coagulation interactions, in relation to blood flow dynamics. We list over 40 studies with genetically modified mice showing a role of platelet and plasma proteins in the control of thrombus stability after vascular injury. These include multiple platelet adhesive receptors and other junctional molecules, components of the ADP receptor signalling cascade to integrin activation, proteins controlling platelet shape, and autocrine activation processes, as well as multiple plasma proteins binding to platelets and proteins of the intrinsic coagulation cascade. Regulatory roles herein of the endothelium and other blood cells are recapitulated as well. Patient studies support the contribution of platelet- and coagulation activation in the regulation of thrombus stability. Analysis of the factors determining flow-dependent thrombus stabilization and embolus formation in mice will help to understand the regulation of this process in human arterial disease.

Myocardial flow reserve by Rb-82 cardiac PET improves the selection of patients eligible for invasive coronary angiography

Aim: We asked whether myocardial flow reserve (MFR) by Rb-82 cardiac PET improve the selection of patients eligible for invasive coronary angiography (ICA). Material and Methods: We enrolled 26 consecutive patients with suspected or known coronary artery disease who performed dynamic Rb-82 PET/CT and (ICA) within 60 days; 4 patients who underwent revascularization or had any cardiovascular events between PET and ICA were excluded. Myocardial blood flow at rest (rMBF), at stress with adenosine (sMBF) and myocardial flow reserve (MFR=sMBF/rMBF) were estimated using the 1-compartment Lortie model (FlowQuant) for each coronary arteries territories. Stenosis severity was assessed using computer-based automated edge detection (QCA). MFR was divided in 3 groups: G1:MFR<1.5, G2:1.5≤MFR<2 and G3:2≤MFR. Stenosis severity was graded as non-significant (<50% or FFR ≥0.8), intermediate (50%≤stenosis<70%) and severe (≥70%). Correlation between MFR and percentage of stenosis were assessed using a non-parametric Spearman test. Results: In G1 (44 vessels), 17 vessels (39%) had a severe stenosis, 11 (25%) an intermediate one, and 16 (36%) no significant stenosis. In G2 (13 vessels), 2 (15%) vessels presented a severe stenosis, 7 (54%) an intermediate one, and 4 (31%) no significant stenosis. In G3 (9 vessels), 0 vessel presented a severe stenosis, 1 (11%) an intermediate one, and 8 (89%) no significant stenosis. Of note, among 11 patients with 3-vessel low MFR<1.5 (G1), 9/11 (82%) had at least one severe stenosis and 2/11 (18%) had at least one intermediate stenosis. There was a significant inverse correlation between stenosis severity and MFR among all 66 territories analyzed (rho= -0.38, p=0.002). Conclusion: Patients with MFR>2 could avoid ICA. Low MFR (G1, G2) on a vessel-based analysis seems to be a poor predictor of severe stenosis severity. Patients with 3-vessel low MFR would benefit from ICA as they are likely to present a significant stenosis in at least one vessel.

The renal hemodynamic effects of ibuprofen in the newborn rabbit.

In early childhood, nonsteroidal anti-inflammatory drugs are mainly used to either prevent or treat premature labor of the mother and patent ductus arteriosus of the newborn infant. The most frequently used prostaglandin-synthesis inhibitor is indomethacin. Fetuses exposed to indomethacin in utero have been born with renal developmental defects, and in both the unborn child and the term and premature newborn this drug may compromise renal glomerular function. The latter has in the past also been observed when i.v. indomethacin or i.v. acetylsalicylic acid (aspirin) were administered to newborn rabbits. The present experiments were designed to evaluate whether ibuprofen has less renal side effects than indomethacin, as claimed. Three groups of anesthetized, ventilated, normoxemic neonatal rabbits were infused with increasing doses of ibuprofen (0.02, 0.2, 2.0 mg/kg body weight) and the following renal parameters were measured: urine volume, urinary sodium excretion, GFR, and renal plasma flow. Renal blood flow, filtration fraction, and the renal vascular resistance were calculated according to standard formulae. Intravenous ibuprofen caused a dose-dependent, significant reduction in urine volume, GFR, and renal blood flow with a fall in filtration fraction in the animals receiving the highest dose of ibuprofen (2 mg/kg body weight). There was a very steep rise in renal vascular resistance. Urinary sodium excretion decreased. These experiments in neonatal rabbits clearly show that acute i.v. doses of ibuprofen also have significant renal hemodynamic and functional side effects, not less than seen previously with indomethacin.

Renal effects of selective cyclooxygenase-2 inhibition in normotensive salt-depleted subjects.

PURPOSE: To compare the renal hemodynamic and tubular effects of celecoxib, a selective inhibitor of cyclooxygenase-2 (COX-2) to those of naproxen, a nonselective inhibitor of cyclooxygenases in salt-depleted subjects. METHODS AND SUBJECTS: Forty subjects were randomized into four parallel groups to receive 200 mg celecoxib twice a day, 400 mg celecoxib twice a day, 500 mg naproxen twice a day, or a placebo for 7 days according to a double-blind study design. Blood pressure, renal hemodynamics, and urinary water and electrolyte excretion were measured before and for 3 hours after drug intake on days 1 and 7. RESULTS: Celecoxib had no effect on systemic blood pressure, but short-term transient decreases in renal blood flow and glomerular filtration rate were found with the highest dose of 400 mg on day 1. On the first day, both celecoxib and naproxen decreased urine output (P < .05) and sodium, lithium, and potassium excretion (P < .01). On day 7, similar effects on water and sodium excretion were observed. During repeated administration, a significant sodium retention occurred during the first 3 days. CONCLUSION: In salt-depleted subjects, selective inhibition of COX-2 causes sodium and potassium retention. This suggests that an increased selectivity for COX-2 does not spare the kidney, at least during salt depletion.