Effects of renal denervation on renal pelvic contractions and connexin expression in rats.

AIMS: The renal pelvis shows spontaneous rhythmic contractile activity. We assessed to what extent this activity depends on renal innervation and studied the role of connexins in pelvic contractions. METHODS: Rats underwent unilateral renal denervation or renal transplantation. Renal pelvic pressure and diuresis were measured in vivo. Spontaneous and agonist-induced contractions of isolated renal pelves were investigated by wire myography. Rat and human renal pelvic connexin mRNA abundances and connexin localization were studied by real-time PCR and immunofluorescence respectively. RESULTS: Renal denervation or transplantation increased renal pelvic pressure in vivo by about 60 and 150%, respectively, but did not significantly affect pelvic contraction frequency. Under in vitro conditions, isolated pelvic preparations from innervated or denervated kidneys showed spontaneous contractions. Pelves from denervated kidneys showed about 50% higher contraction frequencies than pelves from innervated kidneys, whereas contraction force was similar in pelves from denervated and innervated kidneys. There was no denervation-induced supersensitivity to noradrenaline or endothelin-1. Renal denervation did not increase pelvic connexin37, 40, 43 or 45 mRNA abundances. Gap junction blockade had no effect on spontaneous pelvic contractile activity. CONCLUSIONS: The denervation-induced effect on pelvic pressure may be the consequence of the enhanced diuresis. The mechanisms underlying the denervation-induced effects on pelvic contraction frequency remain unknown. Our data rule out a major role for two important candidates, by showing that renal denervation neither induced supersensitivity to contractile agonists nor increased connexin mRNA abundance in the pelvic wall.

Circulating adipocyte fatty acid binding protein is increased in chronic and acute renal dysfunction.

BACKGROUND AND AIMS: The adipokine adipocyte fatty acid binding protein (AFABP) is positively associated with the development of the metabolic syndrome, diabetes mellitus, and cardiovascular disease. We hypothesized that AFABP also increases with deteriorating renal function. METHODS AND RESULTS: Serum AFABP levels were quantified by enzyme linked immunosorbent assay in 532 patients with chronic kidney disease (CKD) covering the whole spectrum of estimated glomerular filtration rate (eGFR) categories from G1 to G5 (study population 1). Furthermore, AFABP was measured in 32 patients before and within 30 h after elective unilateral nephrectomy, a model of acute kidney dysfunction (AKD) (study population 2). Moreover, circulating AFABP was investigated in rats undergoing bilateral nephrectomy (BNE) as compared to sham-operated animals. Median serum AFABP levels adjusted for age, gender, and body mass index significantly increased with increasing eGFR category (G1: 22.0 µg/l; G2: 34.6 µg/l; G3: 56.7 µg/l; G4: 95.2 µg/l; and G5: 173.9 µg/l). Furthermore, renal dysfunction remained positively associated with AFABP in multivariate analysis in this cohort. In patients undergoing unilateral nephrectomy, AFABP increased significantly after surgery (42.1 µg/l) as compared to pre-surgical values (29.3 µg/l). Furthermore, relative changes of post-to-pre-surgical AFABP levels were independently associated with relative changes of post-to-pre-surgical creatinine concentrations. After BNE in rats, AFABP increased significantly as compared to sham-operated animals. CONCLUSIONS: We show that AFABP is significantly elevated in CKD and AKD patients. Furthermore, measures of renal function are associated with circulating AFABP. Moreover, animal experiments indicate that AFABP levels strongly depend on renal function.

[Hypertension and the sympathetic nervous system - recent developments in research and treatment]. / Bluthochdruck und sympathisches Nervensystem - neue Entwicklungen in Forschung und Therapie.

The sympathetic nervous system importantly contributes to the control of the circulation and is an important therapeutic target to lower arterial pressure in hypertensive patients. Recent advances in the understanding of the organization of adrenergic receptors in multiprotein complexes have improved our understanding of arterial pressure control and may have impact on drug development and genetic research in the field of hypertension. New developments in biomedical technology allow for non-pharmacological interventions to reduce sympathetic activity and provide new options to treat hypertensive patients who are resistant to antihypertensive drug therapy.

Low NaCl intake elevates renal medullary endothelin-1 and endothelin A (ETA) receptor mRNA but not the sensitivity of renal Na+ excretion to ETA receptor blockade in rats.

AIMS: This study was performed to investigate the effects of NaCl intake on renal mRNA expression of pre-pro-endothelin-1 (ET-1), endothelin A (ET(A)) and endothelin B (ET(B)) receptors as well as on renal ET-1 content in rats. We further tested for NaCl intake-dependent differences in the contribution of the ET system to renal sodium handling. METHODS: Male Sprague-Dawley rats with telemetric devices were randomized to 0.15%, 0.60% and 1.80% NaCl diets with or without losartan. Renal sodium balance and arterial pressure were monitored. Renal blood flow and fractional sodium excretion (FENa) were measured in response to acute infusion of ET(A) and ET(B) blockers into the inner stripe of the outer renal medulla. RESULTS: Medullary pre-pro-ET-1, ET(A) and ET(B) receptor mRNA was 50%, 81% and 33% higher in rats on 0.15% vs. 1.80% NaCl. Losartan reduced medullary gene expression in rats on 0.15% NaCl. Medullary ET-1 content was 983 +/- 88 and 479 +/- 42 ng mg(-1) protein in rats on 0.15% and 1.80% NaCl (P < 0.001). Chronic ET(A) receptor blocker treatment reduced arterial pressure by 8-10 mmHg in rats on 0.15% vs. 1.80% NaCl without affecting renal sodium balances. Acute medullary ET(A) or ET(B) receptor blockade did not alter medullary blood flow and FENa in animals on either diet. CONCLUSION: In rats renal medullary ET-1 content and mRNA expression of three ET system components are inversely related to NaCl intake. Higher expression levels on low NaCl intake are AT(1) receptor dependent but are not associated with increased sensitivity of renal sodium handling to ET(A) receptor blockade.

Sympathetic reinnervation of rat kidney grafts.

BACKGROUND: Reinnervation occurs in many transplanted tissues and organs. Sympathetic reinnervation in rat kidney grafts was investigated. METHODS: Rats were syngeneically transplanted with a kidney and bilaterally nephrectomized. Reinnervation was assessed by immunohistochemical staining for neuron-specific protein gene product 9.5 (PGP 9.5) and by tissue norepinephrine measurements in grafts removed 1.5 (n=6), 3 (n=7), 6 (n=8), and 9 (n=7) months after transplantation. RESULTS: PGP 9.5-positive neural structures were significantly reduced in grafts removed 1.5 and 3 months after transplantation compared with native kidneys with slightly increased numbers at 6 and 9 months after transplantation. Median transplant norepinephrine concentrations remained at approximately 3% compared with native kidneys until 9 months after transplantation. CONCLUSIONS: In transplanted rat kidneys, some reinnervation occurs in the hilum within 9 months after transplantation. This is not accompanied by a significant recovery of norepinephrine concentration in renal tissue indicating persistent sympathetic denervation.

Sympathetic activity in early renal posttransplantation hypertension in rats.

The contribution of elevated sympathetic activity to the development of renal posttransplantation hypertension was investigated. F1 hybrids (F1H) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were transplanted with either an SHR or an F1H kidney and bilaterally nephrectomized. Three weeks after transplantation, sympathetic activity was assessed by measuring adrenal tyrosine hydroxylase (TH) mRNA content and recording splanchnic nerve activity (SNA) in conscious animals. To investigate the dependence of arterial pressure on sympathetic activity, animals were treated with the alpha(2)-adrenoceptor agonist guanabenz intracerebroventricularly. Mean arterial pressure (MAP) was 143 +/- 4 mmHg in recipients of an SHR kidney (n = 15) versus 110 +/- 3 mmHg in recipients of an F1H kidney (n = 10; P < 0.001). Adrenal TH mRNA content was 1.93 +/- 0.15 fmol/microg total RNA in recipients of an SHR kidney versus 1.96 +/- 0.17 fmol/microg total RNA in recipients of an F1H kidney (not significant). SNA did not differ significantly between recipients of an SHR kidney (n = 8) and recipients of an F1H kidney (n = 7) in terms of frequency and amplitude of synchronized nerve discharges. In response to cumulative intracerebroventricular administration of 10 and 20 microg guanabenz, SNA fell to 51 +/- 5% of control in recipients of an SHR kidney versus 44 +/- 6% of control in recipients of an F1H kidney (not significant) accompanied by a slight fall in MAP in either group. The results suggest that elevated sympathetic activity is not a major contributor to the development of renal posttransplantation hypertension.

Sodium homeostasis in transplanted rats with a spontaneously hypertensive rat kidney.

Recipients of a kidney from spontaneously hypertensive rats (SHR) but not from normotensive Wistar-Kyoto rats (WKY) develop posttransplantation hypertension. To investigate whether renal sodium retention precedes the development of posttransplantation hypertension in recipients of an SHR kidney on a standard sodium diet (0.6% NaCl), we transplanted SHR and WKY kidneys to SHR x WKY F1 hybrids, measured daily sodium balances during the first 12 days after removal of both native kidneys, and recorded mean arterial pressure (MAP) after 8 wk. Recipients of an SHR kidney (n = 12) retained more sodium than recipients of a WKY kidney (n = 12) (7.3 +/- 10 vs. 4.0 +/- 0.7 mmol, P < 0.05). MAP was 144 +/- 6 mmHg in recipients of an SHR kidney and 106 +/- 5 mmHg in recipients of a WKY kidney (P < 0.01). Modest sodium restriction (0.2% NaCl) in a further group of recipients of an SHR kidney (n = 10) did not prevent posttransplantation hypertension (MAP, 142 +/- 4 mmHg). Urinary endothelin and urodilatin excretion rates were similar in recipients of an SHR and a WKY kidney. Transient excess sodium retention after renal transplantation may contribute to posttransplantation hypertension in recipients of an SHR kidney.

The development of post-transplantation hypertension in recipients of an SHR kidney is independent of reinnervation of the graft.

The role of sympathetic reinnervation of kidney grafts for the development of renal post-transplantation hypertension was investigated. F1-hybrids (F1H) obtained from crossing spontaneously hypertensive (SHR) and Wistar-Kyoto rats were transplanted with an SHR kidney and bilaterally nephrectomized. Seven (n = 7) and 42 days after transplantation (n = 9), transplanted kidneys were removed and renal norepinephrine concentrations were determined. In addition, mean arterial pressure (MAP) was measured in conscious bilaterally nephrectomized recipients of an SHR (n = 9) or F1H kidney (n = 8) 6 weeks after transplantation. Renal norepinephrine concentrations (ng/g wet kidney weight) decreased dramatically from 348.3 +/- 31.7 ng/g before (n = 7) to 9.9 +/- 2.5 ng/g at 7 days and 6.5 +/- 1.1 ng/g at 42 days after transplantation, indicating that there was no substantial sympathetic reinnervation of the grafts throughout the observation period. Despite the lack of reinnervation of the grafts, recipients of an SHR kidney but not recipients of an F1H kidney developed post-transplantation hypertension (MAP 172 +/- 4 mmHg versus 124 +/- 3 mmHg P < 0.001) within 6 weeks after transplantation. We conclude that post-transplantation hypertension in recipients of an SHR kidney does not depend on sympathetic reinnervation of the graft.

Influence of arterial baroreceptors and intracerebroventricular guanabenz on synchronized renal nerve activity.

The contributions of changes in the number of active fibres and the peak interval of synchronized neural discharges to arterial baroreflex regulated alterations in renal sympathetic nerve activity were examined in intact conscious rats. Stimulation of central nervous system alpha 2 adrenoreceptors with intracerebroventricular guanabenz (10, 20, 40 micrograms) was used to alter renal sympathetic nerve activity by a non-reflex mechanism in both intact and sinoaortic denervated (SAD) rats. Synchronized renal sympathetic nerve discharge was analysed with the sympathetic peak detection algorithm. When arterial pressure was increased from 50 mmHg to 150 mmHg in intact rats, the peak height (number of simultaneously active fibres) of synchronized discharges decreased in a sigmoidal fashion while the peak interval remained unchanged. Guanabenz produced a dose dependent inhibition of renal sympathetic nerve activity due to both a decrease in peak height and an increase in peak interval of synchronized discharges in both intact and SAD rats. Arterial baroreflex mediated changes in renal sympathetic nerve activity are due to changes in the number of simultaneously active nerve fibres. Central nervous system alpha 2 adrenoreceptor stimulation decreases renal sympathetic nerve activity by decreasing the number of active fibres and increasing the peak interval, acting on additional neural pathways not involved in buffering acute arterial pressure changes.

Cardiopulmonary baroreflex in NaCl-induced hypertension in borderline hypertensive rats.

Borderline hypertensive rats fed an 8% NaCl diet develop increased arterial pressure in association with increased cardiopulmonary baroreflex sensitivity compared with rats fed a 1% NaCl diet. We performed experiments to localize the site of sensitization within the cardiopulmonary baroreflex. To determine whether decreased cardiopulmonary baroreflex sensitivity, as seen in other models of NaCl-induced hypertension, develops later in the course of the disease, we studied an older backcross population derived from borderline hypertensive rats and Wistar-Kyoto rats. Anesthetized borderline hypertensive rats fed 1% and 8% NaCl diets were volume-loaded while right atrial pressure, afferent vagal nerve activity, and renal sympathetic nerve activity were recorded. In 28- to 30-week-old backcross rats fed an 8% NaCl diet, renal sympathetic nerve activity, natriuresis, and diuresis were measured before and during volume loading. Renal sympathetic nerve activity was analyzed with the sympathetic peak detection algorithm. Increases in afferent vagal nerve activity and renal sympathoinhibition were similar in borderline hypertensive rats on either diet during a right atrial pressure rise of 3 mm Hg. In backcross rats, correlations between arterial pressure and renal sympathoinhibition, natriuresis, or diuresis were not found. During volume loading, the peak height of synchronized renal sympathetic nerve discharges decreased while their frequency increased. Attenuated renal sympathoinhibition during acute increases in intravascular volume is not involved in the development or maintenance of NaCl-induced hypertension in borderline hypertensive rats. Renal sympathetic nerve activity decreases because of a reduction in the number of active renal sympathetic nerve fibers.

Effects of acute hypoxia and hyperoxia on ventilation in spontaneously hypertensive and normotensive rat.

The aim of this study was to investigate whether there are differences between particular characteristics of the ventilatory responses to acute hypoxia and hyperoxia in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Pneumotachographic monitoring of ventilation was carried out in anesthetized, spontaneously breathing, normotensive randomly bred Wistar rats (NWR), Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). Under air breathing conditions, minute ventilation in SHR (50 +/- 2 ml/min per 100 g) was not significantly different from that of WKY (54 +/- 3 ml/min per 100 g) but NWR had a significantly lower minute ventilation (39 +/- 1 ml/min per 100 g) than both SHR and WKY. Our data indicate that there is no elevation of the ventilatory drive under air breathing conditions which can be unequivocally associated with primary hypertension in adult animals. During acute hypoxia, minute ventilation increased by a similar magnitude in SHR and NWR (by 97 and 77%, respectively, above baseline values), whereas in WKY the increase was only 58%. When exposed to acute hyperoxia, minute ventilation was inhibited by a similar degree in all animals investigated. We conclude that there is no characteristic pattern of peripheral chemoreceptor-mediated ventilatory responses in close association with primary hypertension.

Cardiorespiratory responses to acute hypoxia and hyperoxia in adult and neonatal spontaneously hypertensive and normotensive rats.

The aim of this study was to investigate whether there are differences between particular characteristics of breathing regulation in primary hypertensive and normotensive states which might indicate significant differences in arterial chemoreceptor reflex function. Under air-breathing conditions, minute ventilation was similar in adult spontaneously hypertensive rats (SHR) (50 +/- 2ml/min x 100 g) and in Wistar-Kyoto rats (WKY) (54 +/- 3 ml/min x 100 g) but significantly lower in randomly bred normotensive Wistar rats (NWR) (39 +/- 1 ml/min x 100 g). In seven-day-old rats minute ventilation was 10.5 +/- 1.2ml/min x 10 g in SHR and 10.2 +/- 1.4 ml/min x 10 g in WKY. Our data indicate that there is no elevation of the ventilatory drive under air-breathing conditions which can be unequivocally associated with primary hypertension in adult and neonatal animals. Acute inhibition of ventilation caused by hyperoxia indicated that oxygen dependent peripheral chemoreceptor activity during air-breathing was similar in SHR and normotensive controls both in the unanesthetized neonatal state and in anesthetized adult animals. No well defined association between the characteristics of the hypoxic ventilatory response and primary hypertension could be demonstrated although responses in adult anesthetized SHR tended to be faster and of higher amplitude than in normotensive controls.

The activity of gamma-glutamyl transpeptidase (gamma-GT) in populations of mononuclear cells from human peripheral blood.

The activity of gamma-glutamyl transpeptidase (EC 2.3.2.2) was observed in populations of non-stimulated mononuclear cells of human peripheral blood selected with antibody-coated magnetic particles. The highest activities of gamma-GT were found in monocytes (7.3-20.0 pkat/10(6) cells). The examination of T lymphocytes revealed a significant difference between CD4-positive (4.1 pkat/10(6) cells) and CD8-positive cells (1.2 pkat/10(6) cells). B lymphocytes and NK cells showed the lowest activities of 0.3 and 1.3 pkat/10(6) cells, respectively. The obvious differences in gamma-GT activities demonstrated here may reflect different biochemical capacities of these cell types, related to their distinct functions in the immune system.