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Compliance is an important property of the arterial system and abnormalities in compliance can greatly affect cardiovascular function. The elastic properties of the common carotid artery were therefore studied in 24 normotensive hemodialysis patients and 24 healthy normotensives using a noninvasive technique. The hemodialysis patients and the control subjects were matched for blood pressure. Arterial distension was measured by Doppler analysis of the vessel wall movements and blood pressure was recorded by finger-phlethysmography (Finapres). The vessel wall distensibility (DC: 2.49 +/- 0.23 10(-3)/mm Hg; mean +/- SEM) was significantly reduced and the end diastolic diameter (d: 7.3 +/- 0.3 mm) was significantly increased in younger hemodialysis patients (36.3 +/- 2.0 years) when compared with age-related controls (DC: 3.44 +/- 0.24 10(-3)/mm Hg; d: 6.3 +/- 0.3 mm; mean +/- SEM). In older hemodialysis patients (60.2 +/- 2.3 years), there was no significant difference in vessel wall distensibility (DC: 1.55 +/- 0.15 10(-3)/mm Hg) and vessel diameter (d: 7.8 +/- 0.3 mm) as compared with age-matched controls (DC: 1.77 +/- 0.14 10(-3)/mm Hg; d: 7.2 +/- 0.3 mm). The results show that vessel wall distensibility of the common carotid artery is decreased in younger hemodialysis patients as compared with age-matched healthy subjects. The volume expanded state in hemodialysis patients cannot account for the decreased arterial distensibility, since volume depletion by hemodialysis was not associated with a significant change of arterial distensibility (DC 2.14 +/- 0.44 10(-3)/mm Hg before, DC 2.26 +/- 0.45 10(-3)/mm Hg after ultrafiltration, NS).(ABSTRACT TRUNCATED AT 250 WORDS)

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Monocyte apoptosis in vitro was studied in patients on long-term hemodialysis, CAPD, and in predialytic uremia to gain insight into the high susceptibility of these patients to infections. Monocytes from dialysis and control subjects were cultured for 24 to 120 hours in vitro to analyze the level and progression of DNA fragmentation as a hallmark of apoptosis. After an incubation time of 48 hours chromatin fragmentation of 48.5 +/- 7.7% was found in monocytes from dialysis patients, which significantly exceeded DNA fragmentation of control monocytes (23.1 +/- 9.1%; N = 12; P < 0.01). Over longer culture periods of up to 5 days, a continuous progression of apoptosis occurred with a similar slope of percent DNA fragmentation in the two studied groups. Monocyte viability was > 95% both in the dialysis and control group. Hemodialysis patients also showed elevated levels of monocyte apoptosis when programmed cell death was evaluated by transmission electron microscopy or DNA electrophoresis of cleaved chromatin. To test the functional relevance of monocyte apoptosis, a significant reduction of Candida growth inhibition by monocytes of dialysis patients was found with a strong linkage between percentage of DNA fragmentation and impaired microbicidal capacity. Monocytes obtained from patients after the hemodialysis session and from CAPD patients showed normal DNA fragmentation levels similar to controls. Differences of monocyte apoptosis between patients on cuprophane and high-flux polysulphone dialysis were not found. Uremic predialytic patients also exerted an increased monocyte DNA fragmentation of 44.2 +/- 1.5% (N = 7; P < 0.05 compared to controls). Enhanced apoptosis of uremic monocytes was accompanied by a reduced formation of TNF-alpha over 48 hours, revealing a significant negative correlation between chromatin fragmentation and monokine synthesis. Supplementation of monocyte cultures from dialysis patients with exogenous TNF-alpha turned increased apoptosis back to baseline levels, suggesting that inflammatory mediators may modulate monocyte senescence. In summary, the elevated degree of monocyte apoptosis in end-stage renal failure may contribute to the impaired cellular host defense seen in these patients.

A transgenic rat line, TGR(mREN2)27, was established by introducing the murine Ren-2 gene into the genome of rats by microinjection techniques. These rats exhibit severe hypertension, making them an interesting model in which to study the role of renin in the pathophysiology of hypertension. However, although the additional renin gene is the only genetic difference compared with control rats, the exact mechanism of hypertension in TGR(mREN2)27 rats is still unclear. It cannot be attributed to a stimulation of the endocrine renin-angiotensin system or to an overexpression of renin in the kidney, since plasma and kidney renin and renin gene expression in the kidney are low in these animals. Here we describe recent progress made toward elucidating mechanisms of hypertension in TGR(mREN2)27 rats. 1) TGR(mREN2)27 rats were bred to homozygosity. The development of high blood pressure in homozygous rats is accelerated compared with that of heterozygous rats. This is paralleled by a higher mortality rate in homozygous TGR(mREN2)27 rats. Blood pressure and mortality rate of homozygous transgenic rats were effectively reduced by 10 mg captopril per kilogram body weight. 2) Treatment of 8-week-old heterozygous TGR(mREN2)27 rats with 10 mg/kg body wt per day of the angiotensin II receptor antagonist DuP 753 for 4.5 weeks normalized blood pressure. After withdrawal of the drug, blood pressure increased rapidly, reaching control levels after 3 weeks. In another group of TGR(mREN2)27 rats treated with 0.5 mg/kg per day, there was no change in blood pressure. Plasma renin and plasma angiotensin II were significantly higher in the high-dose group compared with the low-dose group. These data indicate that angiotensin II plays a major role in hypertension of TGR(mREN2)27 rats. 3) Because the activity of the plasma renin-angiotensin system is reduced in TGR(mREN2)27 rats but the pharmacological interventions with captopril and DuP 753 suggest an important role of angiotensin II for hypertension, our interest focused on tissue renin-angiotensin systems. By Northern hybridization, highest transgene expression was detected in the adrenal gland followed by thymus, tissues of the gastrointestinal and genital tracts, kidney, brain, and lung. No expression was found in the liver and submandibular gland. 4) Compared with Sprague-Dawley rats, urinary glucocorticoid and mineralocorticoid excretion was significantly enhanced in TGR(mREN2)27 rats up to an age of 18 weeks, suggesting that corticoids may be involved in the pathogenesis of hypertension in TGR(mREN2)27 rats. Treatment of 4-and 18-week-old TGR(mREN2)27 rats with the mineralocorticoid receptor antagonist spironolactone, however, did not influence blood pressure. The high expression of Ren-2 in the adrenal glands and the corticosteroid excretion analyses point to an important role of a local adrenal renin-angiotensin system in the pathophysiology of hypertension in TGR (mREN2) or more than two decades, hypertensive rat strains like spontaneously hypertensive rats (SHR) have been use...