Neurohumoral responses to a single haemodialysis in chronic renal patients

The effect of volume reduction on vasoactive substances and their role in estimating dry weight in haemodialysis patients was studied. Plasma atrial natriuretic peptide (ANP), catecholamines, antidiuretic hormone, renin activity and serum aldosterone were measured in 12 patients before and after bicarbonate haemodialysis. Haemodynamical changes were registered and cardiac function and diameter of the inferior vena cava were measured by echocardiography before and after dialysis. Plasma concentration of ANP was significantly reduced by haemodialysis from 209 +/- 51 to 69 +/- 13 pg mL(-1) (n = 12, P < 0.05), whereas concentrations of the other hormones were unchanged. The change in the concentration of ANP did not have significant correlation with weight reduction. The concentration of ANP correlated positively with the diameter of the inferior vena cava (r = 0.70, P < 0.05) after dialysis, but not before dialysis. The concentration of ANP before or after haemodialysis or its change during dialysis did not correlate with any other biochemical parameter. The results show that plasma ANP level is decreased after volume reduction in patients with chronic renal failure, whereas other hormonal systems are unresponsive. However, plasma concentration of ANP seems to have no role in estimating dry weight in chronic haemodialysis patients.     

CNS-induced natriuresis and renal hemodynamics in conscious rats

Sodium excretion was studied following experimental elevation of cerebrospinal fluid (CSF) sodium in heterozygous and homozygous (DI) Brattleboro rats given exogeneous antidiuretic hormone. Sodium excretion increased 4.5-fold in heterozygous and 3.5-fold in DI rats. The natriuresis in both groups was rapid in onset and occurred with a simultaneous kaliuresis. Blood pressure increased approximately 10 mmHg in the heterozygous but not in the DI rats. Accordingly, increased blood pressure may contribute to the natriuresis but is not the sole mechanism. Plasma renin concentration did not change in the DI rats during high Na CSF infusion, and chronic bilateral renal denervation did not abolish the natriuresis. Glomerular filtration rate increased during the high Na period in both the intact and renally denervated rats. These data provide evidence that a natriuretic mechanism exists that is not mediated by changes in antidiuretic hormone, renal nerve activity, mean arterial pressure, aldosterone, or angiotensin II, and thus may be due to another circulating substance or natriuretic hormone. This hormone may act totally or in part by increasing glomerular filtration rate.     

Plasma levels of atrial natriuretic peptide are raised in essential hypertension during low and high sodium intake

Summary Plasma levels of -human atrial natriuretic peptide (hANP) were measured in 17 patients with primary hypertension (11 females, 6 males, aged 22–61; blood pressure systolic 154±7 mmHg, diastolic 92±4 mmHg) and in 9 normotensive controls (4 males, 5 females, aged 20–71; blood pressure systolic 117±4 mmHg, diastolic 76±2 mmHg) during unrestricted sodium diet, at the 4th day of a low sodium intake (40–60 mEq/day) and at the 6th day of sodium loading (280–320 mEq/day) both after an overnight rest and after 4 h of upright posture. In the controls, plasma levels of hANP at 8:00 a.m. were lowered from 73±11 to 49±7 pg/ml during low sodium diet and increased to 128±37 pg/ml after high salt intake. Plasma ANP levels were significantly lower after 4 h of upright posture during unrestricted, low and high sodium intake. In the hypertensive group, plasma ANP levels were elevated during unrestricted diet (203±43 pg/ml), during the low sodium period (139±31 pg/ml), and after high sodium intake (267±63 pg/ml) compared to the controls. All levels were lowered by upright posture. The absolute decrease was more pronounced compared to the normotensives, the relative decline was similar in both groups. In the hypertensives, plasma ANP levels significantly correlate with systolic and diastolic blood pressure (r=0.468,r=0.448,P<0.05) and with urinary aldosterone during unrestricted diet (r=0.536,P<0.05). There was an inverse correlation between plasma ANP levels and plasma renin concentration during low and high sodium intake (r=–0.469,r=–0.496,P<0.05).These studies demonstrate raised circulating plasma ANP levels in patients with essential hypertension. The modulation of ANP by different sodium intake and by upright posture is maintained similar to the changes in plasma ANP in normotensive controls. Raised ANP levels in the hypertensives are correlated with low renin secretion and high aldosterone excretion. High ANP levels, therefore, might indicate sodium retention in essential hypertension.Abbreviation ANP atrial natriuretic peptide Supported by a grant from Ministerium für Wissenschaft und Forschung, NRW     

Effects of oxytocin in normal man during low and high sodium diets

AIM: We tested the hypothesis that oxytocin in normal man causes natriuresis by means of nitric oxide and/or atrial natriuretic peptide. METHODS: Normal male subjects were investigated after 4 days of sodium controlled diets (30 mmol sodium chloride day(-1), n = 8 or 230 mmol sodium chloride day(-1), n = 6). Oxytocin was infused intravenously (1 pmol kg(-1) min(-1) for 240 min). RESULTS: Mean arterial blood pressure, heart rate and glomerular filtration rate by clearance of chromium-labelled ethylenediaminetetraacetate remained stable. Plasma oxytocin increased from 2 to 3 pg mL(-1) to around 50 pg mL(-1). Oxytocin decreased urine flow (4.2 +/- 0.2--0.75 +/- 0.11 and 4.6 +/- 1.3-1.4 +/- 0.6 mL min(-1), low- and high-salt diet, respectively). During low-salt conditions, oxytocin reduced sodium and potassium excretion (11 +/- 2--4 +/- 2 and 93 +/- 19--42 +/- 3 micromol min(-1), respectively). Plasma renin, angiotensin II, aldosterone and renal excretion of metabolites of nitric oxide (nitrate and nitrite) all decreased. Plasma atrial natriuretic peptide and cyclic guanosine monophosphate were unchanged. A similar pattern was obtained during high-salt conditions but in this case the antinatriuresis was not different from that occurring during the corresponding time control series. CONCLUSIONS: The data reject the hypothesis. In contrast, we found significant antinatriuretic, antikaliuretic and antidiuretic effects, which were not mediated by the renin-angiotensin-aldosterone system, atrial natriuretic peptide, systemic haemodynamics, or processes increasing urinary excretion of metabolites of nitric oxide. The natriuretic effect of oxytocin found in laboratory animals is species-specific.     

Effect of somatostatin on kidney function and vasoactive hormone systems in healthy subjects

Summary The acute effects of i.v. somatostatin (250 mcg bolus followed by 250 mcg/h continuous infusion for two hours) on renal hemodynamics, renal electrolyte and water handling, and urinary excretion of catecholamines and prostaglandins, as well as on plasma concentrations of arginine vasopressin, atrial natriuretic factor, norepinephrine, epinephrine, dopamine, glucagon, and plasma renin activity were studied in seven normal subjects. Somatostatin decreased effective renal plasma flow and glomerular filtration rate, osmotic and free water clearances, urine volume, and sodium and potassium excretion, while urinary osmolality, fractional excretion of sodium, and phosphate excretion increased significantly. Plasma concentrations of arginine vasopressin, atrial natriuretic factor, norepinephrine, epinephrine, and dopamine remained unchanged, while plasma renin activity (3.0±0.25 vs 2.4±0.2 ng AngI/ml/h;p}<0.01) and glucagon levels (40±11 vs 20±16 pg/ml;p}<0.01) decreased. Urinary excretion of norepinephrine, epinephrine, dopamine, PGE₂, and PGF_2alpha was suppressed under somatostatin. A significant positive correlation was found between urinary dopamine and sodium excretion (r=0.7;p}<0.001) and urinary postaglandin E₂ and glomerular filtration (r=0.52;p}<0.01). Without accompanying changes in plasma osmolality and vasopressin concentration significant antidiuresis occurred, suggesting a direct tubular effect of somatostatin. However, the hormone-induced changes are due mainly to the decrease in renal plasma flow. The results demonstrate that somatostatin at supraphysiological doses exerts significant effects on the kidney.Abbreviations PAH paraaminohippuric acid - ANF atrial natriuretic factor - AVP arginine vasopressin - PRA plasma renin activity - ERPF effective renal plasma flow - GFR glomerular filtration rate - TRP tubular reabsorption of phosphate - NE norepinephrine - E epinephrine - DA dopamine - GH growth hormone     

Atrial natriuretic peptide in human urine

Summary A highly sensitive radioimmunoassay to measure atrial natriuretic peptide (ANP) concentration in urine has been established, and its clinical usefulness is presented. ANP in urine was stable at 4° C for several days and was easily measured by our radioimmunoassay. The average ANP excretion in 65 healthy persons was 25.0±1.4 ng/day (mean ± SEM) and the fractional excretion of ANP was 0.7±0.05%. In 14 patients with congestive heart failure, the average ANP excretion was 119.2±29.4 ng/day, which decreased to 53.3±11.0 after successful treatment.Abbreviations ANP atrial natriuretic peptide - hANP human atrial natriuretic peptide - RIA radioimmunoasay - NSB non specific bound - FE_ANP the fractional excretion of atrial natriuretic peptide - FE_Na the fractional excretion of sodium - SIADH the syngrome of inappropriate secretion of antidiuretic hormone     

Plasma concentrations of atrial natriuretic peptide, arginine vasopressin and hormones of the renin-angiotensin system in patients with end-stage renal disease

Plasma concentrations of atrial natriuretic peptide (ANP), arginine vasopressin (AVP), plasma renin activity (PRA) and aldosterone, were measured before and after 3 h of hemodialysis in 9 patients with end-stage renal disease on maintenance hemodialysis. Hormone concentrations were also determined in the same patients on a separate occasion after 1 h of ultrafiltration (UF). Plasma concentrations of ANP were significantly higher in the patients with ESRD than in a normal reference population and declined after both 1 h and 3 h of hemodialysis. Plasma concentrations of ANP failed to exhibit a significant decline after 1 h of UF. Plasma AVP concentrations were not significantly different after either hemodialysis or UF, while plasma aldosterone concentrations fell with hemodialysis. The decline in plasma aldosterone concentrations paralleled the decrease in dialysis-induced fall in serum potassium concentrations. There was no correlation between the blood pressures, heart rate, interdialytic weight gain and estimated fluid overload and any of the hormones measured except for the plasma renin activity (PRA) which correlated significantly with the systolic blood pressure. The data suggest that ANP may not be a major factor in blood pressure regulation in normotensive patients with ESRD and its elevation in patients with ESRD is most likely due to fluid overload and atrial distention as well as a possible reduction in its metabolic clearance in renal insufficiency. The fall in plasma ANP following hemodialysis is not due to its removal by dialysis but is most likely due to a reduction in ANP production caused by dialysis-induced correction of hypervolemia.     

Atrial natriuretic peptide, renin activity, aldosterone, urine volume and electrolytes during a 24-h sleep-wake cycle in man

To investigate the diurnal variation in the plasma atrial natriuretic peptide (ANP) concentrations and its relation to renin activity, aldosterone, urine volume and electrolytes, blood samples from six healthy male subjects were collected and blood pressure and heart rate recorded every 4 h during a 24-h sleep-wake period. Systolic blood pressure and heart rate were at the lowest during sleep. Plasma ANP, extracted on Sep-Pak cartridges and measured by radioimmunoassay, had the highest concentration at midnight and lowest at 04.00 h (27 +/- 18 vs 16 +/- 18 ng l-1, mean +/- SD, P less than 0.05 after normalization of the original values). Plasma renin activity and aldosterone were at the highest at 08.00 and 12.00 h, whereafter they both began to decrease (P less than 0.001, also normalized). Urinary volume, sodium, potassium and chloride showed highest values (P less than 0.05) between 08.00 and 16.00 h. Plasma ANP levels did not correlate with systolic blood pressure, heart rate, serum or urinary Na or plasma renin or aldosterone (r = 0.1-0.3, P greater than 0.05). Plasma renin activity correlated with aldosterone and aldosterone with urinary K (r = 0.66 and 0.58 respectively, P less than 0.001). These results suggest that the low plasma ANP levels found in our subjects at 04.00 h may be associated to diminished atrial distension accompanied by the inactivity of the sleep period. In addition, ANP does not appear to affect the secretion of renin and aldosterone in a normal sleep-wake cycle.     

Atrial natriuretic hormone, the renin-aldosterone axis, and blood pressure-electrolyte homeostasis

The renin-angiotensin-aldosterone axis exerts major control over sodium and potassium balance and arterial blood pressure. These three functions are continuously regulated by changes in angiotensin II and aldosterone levels in response to wide variations in dietary intake of sodium and potassium. In addition, changes in intrarenal physical factors cause changes in the supply of distal tubular sodium that, in turn, work to determine sodium and potassium excretion and to modulate the release of renal renin. However, certain aspects of sodium homeostasis cannot be fully explained either by the activity of the renin system or by intrarenal physical factors, and this has led investigators to search for other natriuretic hormonal mechanisms. Recently, it has become clear that atrial tissue contains a group of peptides, at least one of which is probably secreted as a regulatory hormone. In animals, these atrial peptides produce immediate, marked natriuresis associated with a rise in glomerular filtration rate (but no alteration of total renal flow) and a simultaneous decrease in arterial blood pressure. Atrial peptides also inhibit renal renin secretion and adrenal cortical secretion of aldosterone, and they oppose the vasoconstrictive action of angiotensin II. One of these atrial peptides may therefore be the long-sought natriuretic hormone, though in a different form and shape than was envisioned. The fact that atrial peptide works to oppose the renin system at four points suggests that this new hormone could have a major complementary role in long-term regulation of blood pressure and electrolyte homeostasis. In this construction the renin system primarily defends sodium balance and blood pressure, with the atrial hormone having an increasing counter-influence in situations involving high blood pressure or sodium surfeit. We can soon expect to learn more about this atrial hormone, including which peptide is the active circulating hormone, what induces or inhibits its release, and what part it plays in cardiovascular diseases.     

Children in sauna: hormonal adjustments to intensive short thermal stress

Hormonal response to Finnish sauna bath was investigated in 20 prepubertal children (age 5-10 years). Blood leukocyte count, plasma potassium, serum aldosterone, growth hormone and prolactin concentrations increased; plasma volume, plasma sodium, catecholamines, serum antidiuretic hormone, atrial natriuretic peptide (ANP), cortisol, and thyrotropin concentrations remained unchanged during sauna bath. One hour after sauna, serum thyrotropin, atrial natriuretic peptide and blood glucose concentrations decreased, whereas the rest of the hormones remained unchanged. Our results implicate that maintenance of homeothermia resulted in moderate hormonal changes in children during Finnish sauna bath which indicate similar adequate hormonal thermoregulatory adjustment as previously documented in adults.     

Responses of atrial natriuretic peptide and other fluid regulating hormones to long distance swimming in the sea

The plasma hormonal response following a swimming competition in the sea (18 km) was evaluated in 12 top level male endurance swimmers. At the end of the effort, while plasma renin activity (PRA) and aldosterone concentration (ALDO) were unchanged, a significant increase in plasma atrial natriuretic peptide (ANP) and antidiuretic hormone (ADH) concentrations were recorded. These changes were associated with a decrease in haematocrit and an increase in Na⁺ and Cl^– plasma concentrations. The individual variations of ANP (difference between the final and initial concentrations) were inversely correlated with the corresponding individual variations of PRA and ADH. The results suggest that, during prolonged swimming, ANP may exert an inhibitory effect on the PRA-ALDO axis and have a modulatory role with regard to ADH secretion.     

Atrial natriuretic peptide secretion in heart transplant patients

Plasma atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (ALD) and vasopressin (VP) were assessed in six heart transplant patients (HTP) and ten healthy subjects under bed rest conditions and 60 and 120 minutes after head-out water immersion (WI). Bed rest had no significant influence on these parameters. WI raised plasma volume (PV) to the same extent in both groups. This increase of PV was accompanied by significant suppression of PRA, ALD and VP and an increase of plasma ANP. In HTP basal plasma ANP was significantly elevated and the ANP response to central hypervolemia reduced. Significantly elevated VP plasma levels were also found in HTP. These endocrine abnormalities in HTP seem to be caused by latent failure of the transplanted heart. No direct correlation was found between plasma ANP and PRA, ALD and VP under basal conditions and after WI in either HTP or normals.     

Naloxone in treatment of circulatory shock resistant to conventional therapy

Summary The effect of naloxone (4.4–5.9 mg i.v.) was evaluated in 10 patients with circulatory shock (sepsis,n=7; intoxication,n=1; cardiogenic shock,n=2) not responding to full conventional therapy. In addition, we measured plasma ACTH and immunoreactive -endorphin before and 60 min after administration of naloxone and compared the results with hormone concentrations in 10 intensive care patients without shock. Only in two patient with septic shock a transient increase (duration 15 min and 60 min, respectively) of systolic blood pressure was observed, while naloxone was ineffective in the remaining eight patients. No adverse effects of naloxone were found. Plasma ACTH and immunoreactive -endorphin concentrations in patients with shock were not different from those in controls (ACTH, 79±28 vs 120±60 pg/ml; immunoreactive -endorphin, 952±262 vs 1,070±378 pg/ml).Our findings suggest that naloxone in a single dose of 4.4–5.9 mg i.v. does not improve the management of circulatory shock unresponsive to conventional treatment. -endorphin seems to play no major role in the hypotension of shock.Abbreviations ACTH Adrenocorticotrophic hormone - HD intermittent hemodialysis - HF heart rate - ir immunoreactive - RR_syst systolic blood pressure Supported by Landesamt für Forschung, NRW     

Serial plasma concentrations of atrial natriuretic peptide, plasma renin activity, aldosterone, and antidiuretic hormone in neonates on extracorporeal membrane oxygenation

To obtain information on water and salt regulating hormones and volume homeostasis during neonatal extracorporeal membrane oxygenation (ECMO), serial determinations of atrial natriuretic peptide (ANP), plasma renin activity (PRA), aldosterone (Aldo), antidiuretic hormone (ADH), colloid-osmotic pressure (COP), osmolality (Osmol), and central venous pressure (CVP) before, during, and after neonatal ECMO in 10 neonates with meconium aspiration syndrome (MAS) were carried out. Mean gestational ages and birth weights were 41(+3) weeks (39(+6) - 42(+4)) and 4,063 gm (3,500-4700), respectively; mean age at start and duration of ECMO 29.3 (14-69) and 152.6 hr (92-267), respectively. Plasma ANP (mean +/- SD) was 67.8+/-69.1 pmol/L before, decreased to 33.3+/-22.1 (not significant) pmol/L during, and significantly increased to 274.6+/-131.8 pmol/L after ECMO (p < 0.05). ANP correlated positively with CVP (r = 0.63; p < 0.001). Pre-ECMO PRA, Aldo, and ADH were comparable to those described earlier in normal neonates, decreased during (p < 0.001 for Aldo; p < 0.05 for PRA and ADH) and either remained elevated (PRA, p < 0.001; Aldo, p < 0.05) or decreased (ADH) after ECMO. COP and Osmol remained unchanged. Neonatal ECMO for MAS is characterized by circulatory and osmotic equilibrium. It is suggested that circulating volume contracts during and expands after neonatal ECMO for MAS.     

Alterations of vasoconstrictor and sodium-regulating hormone systems in vascularly decompensated liver cirrhosis

Plasma levels of atrial natriuretic peptide (ANP), aldosterone (PA), vasopressin (AVP), and the plasma renin activity (PRA) were examined in 15 vascularly decompensated patients suffering from liver cirrhosis, before and after administration of albumin and after a subsequent administration of furosemide. The initial ANP level was lower in 9 patients (group "A") and higher in 6 patients (group "B") than in healthy controls (Group "A": 19.5 +/- 3.0 fmol/ml; group "B": 36.7 +/- 3.9 fmol/ml; control: 25.8 +/- 2.4 fmol/ml). The initial PRA (4.4 +/- 1.0 ng AngI/ml/h) and AVP (8.5 +/- 1.5 pg/ml) activity in group "A" increased significantly compared to group "B" (PRA: 0.44 +/- 0.09; AVP: 4.1 +/- 0.5), indicating an intravascular volume depletion in group "A". Albumin infusion raised the urine and sodium excretion and the plasma concentration of ANP in group "A" but lowered in plasma levels of renin and vasopressin. The same parameters were not changed by albumin in group "B". Furosemide equally raised the urine flow rate and sodium excretion in both groups. Plasma ANP level depends on the intravascular volume, and the secondary change in its plasma concentration plays a considerable role in the retention of fluid and electrolytes in patients with cirrhosis. The increased intravascular volume in these patients depletes the fluid and electrolyte retention via the increase in ANP level.     

Atrial natriuretic peptide response to physical exercise is inhibited by an antagonist of the opioid receptors

It was been shown that physical exercise increases plasma atrial natriuretic peptide (ANP) level. This effect was attributed to the hemodynamic changes of exercise which could increase atrial volume and result in ANP secretion. On the other hand, it was evidenced that morphine and opiate peptides greatly stimulate ANP release. To evaluate to what extent the endogenous opioid secretion during exercise induces the ANP release, six healthy volunteers male trained subjects were submitted to two maximal exercise tests with and without (placebo) opiate receptors blockade by naltrexone (50 mg per os). Blood samples were drawn before (rest) and after maximal exercise in order to measure by radioimmunological methods human atrial natriuretic peptide (alpha-h-ANP), beta-endorphin, plasma aldosterone (ALD), plasma renin activity (PRA) and corticotrophin (ACTH). Expired gas was collected during exercise to measure oxygen consumption. Subjects reached the same value of maximal oxygen consumption (VO2 max) at the end of exercise whatever treatment. Plasma ANP level at rest decreases slightly after administration of naltrexone (32.8 +/- 6.3 pg/ml with placebo versus 21.3 +/- 4.6 pg/ml with naltrexone) but the response to physical exercise was significantly reduced by naltrexone (73.3 +/- 14.9 pg/ml with placebo versus 46.9 +/- 8.6 pg/ml with naltrexone) (p less than 0.05). There was no statistical difference according to the treatment between the plasma levels of beta-endorphin, PRA and ACTH at rest as well as at the end of a maximal exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of atrial natriuretic peptide in the development of arterial hypertension in patients with pubertal hypothalamic syndrome

The role of a depressor factor, atrial natriuretic peptide, in the development of arterial hypertension in adolescents with pubertal hypothalamic syndrome was studied in 52 patients and 13 healthy males aged 13–24 years. The duration of disease was 2–11 years. Radioimmunological methods were used to measure plasma atrial natriuretic peptide, plasma renin activity, and serum aldosterone. Patients with borderline arterial hypertension were found to have a significant reduction in their atrial natriuretic peptide levels, and this correlated directly with the renin-aldosterone system, demonstrating insufficiency of the depressor system in patients with pubertal hypothalamic syndrome and the involvement of atrial natriuretic peptide in the development of arterial hypertension, along with disturbances in the functional relationship between atrial natriuretic peptide and the renin-aldosterone system. This article was presented at the III All-Russian Congress of Endocrinologists. Samara Medical University. Translated from Problemy éndokrinologii, Vol. 43, No. 4, pp. 21–22, July–August, 1997.     

冠状动脉介入及替罗非班治疗老年急性心肌梗死并 心源性休克的疗效分析

目的 对老年急性心肌梗死并心源性休克患者联合应用经皮冠状动脉介入及替罗非班进行临床治疗。方法 选取2016年8月~2017年8月黑龙江省佳木斯市中心医院共收到符合本次研究要求的老年急性心肌梗死并心源性休克患者40例,按照患者随机数字表法将患者分为观察组及对照组各20例。其中观察组应用经皮冠状动脉介入联合替罗非班治疗,对照组仅用皮冠状动脉介入治疗,比较两组患者的治疗效果。结果 治疗后观察组的治疗效果优于对照组（P＜0.05）;观察组患者LVEF水平高于对照组（P＜0.05）;手术结束后,观察组TIMI值高于对照组患者（P＜0.05）。结论 在对老年急性心肌梗死并心源性休克患者进行治疗的过程中,选取皮冠状动脉介入联合应用替罗非班治疗较为有效,治疗效果显著。     

Renal function and endocrine responses to arm exercise in euhydrated individuals with spinal cord injury

This study investigated the renal and endocrine responses to arm exercise in persons with spinal cord injury (SCI) under euhydration conditions (ad libitum drinking of water) and determined the physiological effects of exercise on renal function in these subjects. Eleven SCI (spinal lesions between T6 and L1, American Spinal Injury Association impairment scale A) and 14 able-bodied (AB) persons first rested for 1 h in a sitting position, before undergoing 2-h arm-crank ergometer exercise at 60% of maximum oxygen consumption followed by a 2-h recovery period. On another day, all subjects participated in a time control study (5 h of rest condition in sitting position). Urine and blood samples were collected hourly. There were no differences in mean blood pressure between the two groups. SCI patients showed attenuated increase in plasma adrenaline and increase in plasma aldosterone compared with AB controls, but similar changes in human atrial natriuretic polypeptide, plasma renin activity and plasma antidiuretic hormone following the exercise. Creatinine clearance, osmolal clearance, free water clearance and fractional excretion of Na⁺ did not change during exercise in any of the subjects. These findings suggested that activated aldosterone and attenuated adrenaline responses during exercise in SCI could be due to adaptation to disordered sympathetic nervous system triggered to maintain renal function. The results showed no exercise-related adverse effects on renal function in hydrated subjects with SCI.     

Effects of estrogen replacement therapy on natriuretic peptides and blood pressure

OBJECTIVE: Estrogen replacement therapy (ERT) has been reported to affect blood pressure. Since natriuretic peptides have natriuretic and vasodilatory activity and also inhibit the renin-angiotensin-aldosterone system and lower blood pressure, it was hypothesized that the changes in blood pressure effected by ERT might be mediated via changes in natriuretic peptides. METHODS: Fifty-eight postmenopausal hysterectomized women were randomized in a double-blind, double-dummy study to receive either peroral estradiol valerate 2 mg/day or transdermal estradiol gel containing 1 mg estradiol/day for 6 months. Blood pressure was measured by using an automatic, oscillometric device. Plasma atrial natriuretic peptide (ANP), N-terminal fragment of proANP (NT-proANP), B-type natriuretic peptide (BNP), aldosterone, and renin were determined by radioimmunoassay. RESULTS: The mean decrease in diastolic blood pressure was -6 mmHg both in the peroral group (n = 26) (P = 0.002) and in the gel group (n = 27) (P = 0.001), and the corresponding decreases in systolic blood pressure were -4 mmHg (P = 0.070) and -7 mmHg (P = 0.028) in the sitting position. Plasma NT-proANP rose from 212 to 264 pmol/l (P = 0.001) on peroral ERT and from 240 to 292 pmol/l (P = 0.008) on transdermal ERT. No significant changes were observed in the plasma ANP, BNP, aldosterone, and renin levels. CONCLUSIONS: Both peroral and transdermal ERT result in elevated plasma levels of NT-proANP, indicating an activation of the natriuretic peptide system. This could explain, at least in part, the lowering of blood pressure during ERT.