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Biomedical subjects

J C Roos

Publications and source records attributed to J C Roos.

At least 91 records · Page 5Linked to original sources
PubMed1985

Renal sodium handling in normal humans subjected to low, normal, and extremely high sodium supplies.

We studied renal sodium handling, extracellular fluid volume (ECFV), plasma renin activity, aldosterone and norepinephrine, and blood pressure in eight healthy volunteers after equilibration on intakes of 20, 200, and 1,128 +/- 141 meq sodium, respectively. Renal sodium handling was assessed by means of clearance studies during maximal water diuresis and lithium clearance. Urinary sodium excretions were 22 +/- 4, 202 +/- 19, and 1,052 +/- 86 meq/day. From the lower to the upper sodium intake level, 24-h creatinine clearance rose from 111 +/- 7 to 136 +/- 11 ml/min and inulin clearance from 103 +/- 9 to 129 +/- 9 ml/min, whereas proximal and distal fractional sodium reabsorption (FSRprox and FSRdist, respectively) fell from 86.8 +/- 1.3 to 79.0 +/- 2.7% and from 96.5 +/- 0.5 to 76.0 +/- 1.9%, respectively. During the normal sodium intake (200 meq), intermediate values were recorded. The changes in fractional lithium clearance were less consistent but correlated with FSRprox (r = 0.78, P less than 0.001) and not with FSRdist. Major changes in plasma renin activity, aldosterone, and, to a lesser extent, norepinephrine accompanied these changes in kidney function, displaying inverse and exponential correlations with daily sodium excretion and ECFV. No consistent rise in blood pressure was detected. These observations indicate that in healthy humans renal adaptation to vast variations in sodium intake includes resetting of glomerular filtration rate, FSRprox, and, in particular, FSRdist. Alterations in neurohumoral factors may play a dominant role in this adaptation.

Absorption↗
PubMed1984

Functional relationships in the nephrotic syndrome.

An analysis of 70 observations in patients with the nephrotic syndrome (NS) on a low sodium diet is presented. The following parameters were determined: plasma volume, plasma renin activity, plasma aldosterone concentration, serum albumin, urinary sodium and protein excretion, and creatinine clearance. In 41 instances glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined on the basis of 51Cr-EDTA and 125I-hippuran clearances, and the filtration fraction (FF) was calculated. The results in patients with minimal lesions (ML) and those with histological glomerular lesions (HL) were compared to determine whether these groups can be separated on the basis of signs of hypovolemia and primary renal sodium retention. Although a higher proportion of the ML patients showed extreme sodium retention and elevated plasma renin and aldosterone levels, these values tended to overlap and no differences were found for blood volume, blood pressure, and overall renal function between the groups. FF was markedly and equally depressed in both groups: 13.5 +/- 1.6% in the ML and 14.2 +/- 1.1% SEM in the HL group (NS). Analysis of the within-group relationships between the parameters under study revealed relatively few correlations, which supports the hypothesis that primary impairment of renal water and salt excretion is an important if not overruling factor in patients with the NS.

Adolescent↗
PubMed1984

Effects of plasma volume expansion on renal salt handling in patients with the nephrotic syndrome.

In 10 patients with the nephrotic syndrome (NS) and edema persisting despite a NaCl-poor diet, the effect of a single infusion of hyperoncotic albumin (75 g) on NaCl excretion was studied. 6 patients had minimal lesions, and 2 patients were studied twice. On half of the occasions the glomerular filtration rate was reduced. Blood volume (BV), calculated from plasma volume and hematocrit, was slightly elevated before infusion, and increased to 136 and 120% of normal at 4 and 20 h after it, respectively. Plasma renin activity (PRA) and plasma aldosterone (PA) both decreased to suppressed levels at 20 h after infusion. Sodium excretion increased from 9.2 +/- 7.6 muEq/min before, to 3.10 +/- 22.4 (0-4 h) and 43.1 +/- 36.3 muEq/min (4-20 h) after infusion. In 6 of these patients clearance studies were done before and after the infusion, maximal free water clearance being used as marker for distal NaCl reabsorption. Proximal fractional NaCl reabsorption was elevated before (94.9 +/- 1.4%) and decreased after the infusion (92.8 +/- 1.7%). Distal fractional NaCl reabsorption was also elevated before (93.0 +/- 6.4%), but unaltered after infusion (93.0 +/- 5.6%). Thus, after marked expansion of BV and suppression of PRA and PA, sodium excretion remained low despite the present edema. The results indicate that in many patients with the NS, including minimal lesion NS, intravascular hypovolemia is not the sole cause of sodium retention.

Absorption↗
PubMed1984

Relation between plasma aldosterone concentration and renal handling of sodium and potassium, in particular in patients with chronic renal failure.

In normal subjects a relation was found between the log plasma aldosterone concentration (PAC) and the ratio of renal potassium excretion (UK) and sodium delivery to the sodium-potassium exchange site (UNa + K). This relationship was independent of plasma renin activity (PRA). On these grounds, the UK/UNa + K ratio disturbance was considered to be a function of the PAC, and this relation was considered to reflect an altered sensitivity of the distal tubule to aldosterone. In several pathological conditions involving the kidney, the relation between the PAC and UK/UNa + K remained normal while the glomerular filtration rate was within normal limits. Under these conditions, however, the serum potassium concentration had some influence on this relation, in that a low potassium concentration was accompanied by an elevated (though still normal) PAC relative to the UK/UNa + K ratio. The relation was completely abolished when the effect of endogenous aldosterone was impaired by chronic renal disease made it possible to classify them according to the pathophysiological disturbance in question. We conclude that determination of the UK/UNa + K ratio and its relation to the PAC, PRA, and serum potassium level is very useful for the analysis of disorders of potassium metabolism.

Adolescent↗
PubMed1984

Intrarenal sodium handling during chronic spironolactone treatment.

Intrarenal sodium handling was studied in 8 patients with essential hypertension before spironolactone treatment (200 mg/day), on the 4th day of treatment, and after 3 months of treatment. The results were compared with similar studies with chlorthalidone (50 mg/day). Renal sodium handling was assessed by simultaneous determination of the glomerular filtration rate, sodium, and potassium excretion, and maximal free-water clearance (CH2O). We took CH2O as an index of 'distal' sodium chloride reabsorption from which the proximal sodium reabsorption was calculated. During the first days of spironolactone treatment a natriuresis and increase in urinary flow rate was found. It resulted in a decrease of the extracellular fluid volume amounting to 0.9 liters and a 2.5-fold increase in the plasma renin activity. Potassium excretion showed a small but significant rise. After 3 months, virtually the same degree of volume depletion was found, which was comparable to that obtained after 3 months of chlorthalidone treatment. CH2O, as a fraction of glomerular filtration rate, decreased by 24% both after 3 days and 3 months, whereas proximal sodium reabsorption increased from 87.8 to 90.4% of the filtered load. CH2O, corrected for the 'distal' delivery of sodium, decreased from 85.3 to 80.7%. These changes were nearly the same as those found after 3 months of chlorthalidone treatment. It is concluded from these calculated values that spironolactone inhibits sodium chloride reabsorption in the diluting segment of the nephron and that the resulting increase in sodium delivery or urinary flow to the potassium excretory site partly counteracts the blocking effect of spironolactone on this part of the nephron, thus increasing potassium excretion during the acute administration of this drug.

Adult↗
PubMed1983

A study on the distribution of body fluids after rapid saline expansion in normal subjects and in patients with renal insufficiency: preferential intravascular deposition in renal failure.

1. The effect of rapid intravenous infusion of 25 ml of isotonic sodium chloride solution (saline)/kg body weight on extracellular fluid volume (ECFV, 82Br distribution volume), plasma volume (131I-labelled albumin distribution volume) and blood volume (from plasma volume and packed cell volume) was studied in nine normal subjects and a group of 11 patients with end-stage renal disease (ESRD). 2. Immediately after the infusion, the increases in ECFV were equal in the two groups but the increases in plasma and blood volumes were significantly larger in the patients with ESRD. 3. Ninety minutes after the end of the infusion, the blood volume/ECFV ratio was significantly decreased from the control value in the normal subjects, but slightly increased in the patients with ESRD. 4. It is concluded that in severe renal failure the control of fluid distribution is changed in a way which leads to a preferential distribution of rapidly infused saline into the intravascular compartment.

Adult↗
PubMed1983

Cardiac effects of antidepressant drugs. A comparison of the tricyclic antidepressants and fluvoxamine.

1 The cardiovascular effects of the tricyclic antidepressants (TCAs) are reviewed and compared with those of fluvoxamine, a new 5-hydroxytryptamine (5-HT) re-uptake inhibitor. 2 The TCAs have important effects on the heart, related to their anticholinergic and quinidine-like properties. The major side effects in therapeutic dosage include heart rate increase, postural hypotension and slight prolongation of the intraventricular conduction time and QT interval. In toxic dosage (or normal dosage in patients with severe heart disease) both advanced heart block and ventricular arrhythmias can occur, together with clinically important loss of myocardial contractile force. 3 Fluvoxamine has no effects on the heart except for a statistically (but not clinically) significant slowing of the heart rate.

Animals↗
PubMed1982

Sulfinpyrazone: an antiarrhythmic drug?

To determine whether a direct antiarrhythmic effect could explain the claimed beneficial effect of sulfinpyrazone on the sudden death rate in postmyocardial infarction patients, we performed a double-blind, randomized trial in 20 patients with impulse-formation and conduction defects. The patients were studied by intracardiac electrocardiography and programmed stimulation before and after an intravenous bolus injection of either 500 mg sulfinpyrazone or a placebo. We found no consistent clinical or statistical effects of sulfinpyrazone on sinus rate, sinus node recovery time, sinoatrial conduction time, conduction intervals during spontaneous cardiac activity and atrial pacing. Wenckebach point and refractory periods of the atrium, AV node, His Purkinje system and right ventricle. We conclude that sulfinpyrazone has no clinical electrophysiological effects comparable with those of known antiarrhythmic agents and that a direct antiarrhythmic action is an unlikely explanation for the reduction of sudden death in postinfarction patients treated with this drug. Antiarrhythmic activity by an indirect mechanism, related to the antiplatelet properties of the drug, or by metabolites of sulfinpyrazone, remains a possibility requiring further investigation.

Arrhythmias, Cardiac↗
PubMed1982

Changes in intrarenal uric acid handling during chronic spironolactone treatment in patients with essential hypertension.

Intrarenal handling of uric acid was studied in 12 patients with essential hypertension under spironolactone treatment (200 mg/day). The degree of volume depletion during treatment was assessed from the changes in body weight and plasma renin activity (PRA). The results are compared with those in patients treated with chlorthalidone (50 mg/day). During spironolactone treatment, the serum uric acid level remained constant despite a progressive volume depletion which after 3 months reached levels identical to those achieved in the chlorthalidone-treated patients, whose serum uric acid level showed the expected rise (21%). The uric acid excretion during spironolactone treatment was markedly diminished (-28%), and thus the 24-hour clearance of uric acid was correspondingly decreased (-22%). It is concluded that spironolactone affects uric acid metabolism in two ways: it causes a decrease in uric acid renal clearance (probably mediated by the induced volume depletion and PRA elevation, as with other saluretics) and, probably, inhibits endogenous uric acid production to approximately the same degree as the clearance is decreased, so that no change in the serum uric acid level occurs. The purpose of the study was to investigate the effect of spironolactone on uric acid handling by the kidney. We found a decrease in uric acid clearance and uric acid excretion. Serum uric acid concentration did not change.

Body Weight↗
PubMed1982

Salt handling in patients with chronic renal insufficiency.

In 7 patients with moderate degrees of renal insufficiency the effect of high and low salt intake on renal NaCl handling was investigated by means of clearance techniques. After a steady state had been reached at low (1 g NaCl daily) and high (10 mmol NaCl daily for every ml X min-1 glomerular filtration rate) salt intake, proximal and distal fractional salt reabsorption (FSRprox and FSRdist) were estimated, maximal free water clearance being taken as an index of distal NaCl reabsorption. Mean FSRprox during low salt intake was 86.7% (range 80-90%) of the filtered load, and decreased to 77.9% (range 70.1-80.5%) during high salt intake. The water-loading procedure in these patients resulted in enhanced NaCl and nonelectrolyte solute excretion, especially during salt restriction. This made certain corrections obligatory for the proper calculation of FSRdist. Mean FSRdist during low salt intake was 96.5% (range 93.1-99.8%) of distal delivery, and decreased to 76.0% (range 68.0-82.1%) during high salt intake. This decrease of FSRdist also existed at comparable levels of distal delivery. It is concluded that renal response to chronic sodium loading in patients with chronic renal insufficiency is similar to that as in normal men, and consists of reduction of both proximal and distal fractional NaCl reabsorption.

Absorption↗
PubMed1981

Determination of glomerular filtration rate by 111In-DTPA.

To evaluate the use of 111indium-diethylenetriamine pentaacetic acid (111In-DTPA) for determination of the glomerular filtration rate (GFR), the results of 60 standard 111In-DTPA clearances were compared with 24-h urine endogenic creatinine clearances obtained on 3 successive days (r = 0.97, P less than 0.001) and with endogenic creatinine clearances obtained during 111In-DTPA determinations (r = 0.93, P less than 0.0001). It is concluded that 111In-DTPA is a useful marker for GFR.

Creatinine↗
PubMed1981

Haemodynamic and hormonal changes during acute and chronic diuretic treatment in essential hypertension.

The short- and long-term effects of diuretic treatment with chlorthalidone 50 mg/day on haemodynamic and hormonal parameters in patients with essential hypertension (WHO grade I) were investigated. After three days of treatment, all patients showed a rise in plasma renin activity (PRA), plasma aldosterone (PA), urinary norepinephrine excretion (UNE) and heart rate (HR), and a decrease in body weight (BW) and extracellular volume (ECV) and blood volume (BV); the change in blood pressure (BP) was variable. The changes in BP were correlated with those in BV. After three months of therapy, the signs of volume depletion tended to fade, but the lower ECV persisted. In contrast to the 4-day study, after three months the change in BP correlated inversely with changes in ECV and renin dependency (saralasin response), and positively with PRA and changes in UNE. It is concluded that the BP response to diuretic treatment is determined by the adaptation with time of the haemodynamic reactions to the volume-depleted state. Whether this adaptation will take place cannot be predicted from the control values of the parameters studied, or from acute changes observed during the first days of treatment.

Adolescent↗
PubMed1981

Changes in intrarenal sodium handling during saluretic treatment in patients with essential hypertension.

The effect of 50 mg chlorthalidone on blood pressure, body fluid volumes and renal functional parameters was determined in 8 patients with essential hypertension. After 3 days there were signs of volume depletion with little change in mean arterial pressure (MAP). Maximal free water clearance (CH2O) was decreased and fractional proximal sodium reabsorption was increased, but no correlations between these parameters were found. After 3 months there was in inverse relationship between both changes in MAP and the indices of volume depletion and CH2O. It is concluded that when MAP decreases after prolonged saluretic treatment, there is a partial recovery of the initially induced volume depletion and less stimulation of proximal tubular sodium reabsorption. The continuing inhibitory action of chlorthalidone on "distal" sodium reabsorption is partially compensated for, probably by the stimulating effect at this site of the decrease in MAP.

Adolescent↗
PubMed1981

Renin and body fluid volumes in chronic renal disease. Relations between arterial pressure, plasma renin activity, blood volume, and extracellular volume in chronic renal disease, as compared with essential hypertension.

In 47 patients with hypertension and chronic renal insufficiency (CRI) and 38 patients with essential hypertension (EH), the following parameters were measured under moderate salt restriction: plasma volume (PV), blood volume (BV), extracellular fluid volume (ECFV), ratio of blood volume to insterstitial fluid volume (BV/IV), recumbent plasma renin activity (PRA), increase in PRA upon standing (delta PRAst), creatinine clearance (Ccr), and mean arterial pressure (MAP). Mean PRA, ECFV, and MAP values did not differ significantly between the two groups. In the CRI group, MAP showed a weak positive correlation with ECFV (r = 0.34). Mean PV, BV and BV/IV ratio were significantly higher than in the EH group, whereas delta PRAst was markedly blunted (p less than 0.001) and showed a weak correlation with Ccr (r = 0.33). This suggests that patients with CRI on a moderate Na intake have a decreased tissue compliance which results in a relative elevation of BV. On the other hand, although MAP was not significantly correlated with either BV or IV, a negative correlation (r = -0.31) was found between MAP and BV/IV, indicating that elevation of the blood pressure (BP) tends to depress BV. These oppositely directed effects may explain the failure so far to establish a relationship between BP in renal disease and any haemodynamic parameter or combination of such parameters.

Blood Pressure↗
PubMed1980

Observations on plasma renin substrate in the nephrotic syndrome.

Literature data on renin in the nephrotic syndrome are conflicting: renin values are reported to be elevated as the rule, but sometimes normal or low; data on renin substrate are scanty and pointing to low values. In the present study, plasma renin activity (PRA) and plasma renin substrates (PRS) were measured in 27 episodes of the nephrotic phase in 24 patients with nephrotic syndrome with various lesions. 10 patients were reinvestigated after remission; 1 patient could be followed during development of the edema phase as well as during prednisone-induced remission. During the nephrotic phase, PRS was suppressed in 8%, normal in 44 and elevated in 48%, while PRA was suppressed in 41%, normal in 48 and elevated in 11% of the patients. After remission, PRA increased in 70% and PRS decreased in 20 and increased in 50% of the cases. The purpose of this study was to investigate PRA and PRS in nephrotic patients; it is concluded that low PRS and high PRA are not as characteristic for the nephrotic syndrome as they are generally thought to be.

Adult↗
PubMed1980

Observations on the blood pressure lowering mechanism of diuretics.

The haemodynamic effects of short-time (3-7 days) and longer (2-3 months) periods of saliuretic treatment were investigated in several groups of patients with uncomplicated essential hypertension. Short-time salt depletion results in decrease of cardiac index, extracellular and blood volumes and marked increases in plasma renin activity (PRA) and noradrenaline excretion, while blood pressure (BP) becomes "renin dependent"as assessed by an angiotensin I antagonist (P 113). The BP decrease was only moderate and variable, due to increased peripheral resistance, and could not be related either to control PRA values or degree of subsequent elevation. After longer treatment periods, all of the above-mentioned changes are still present, but less pronounced while BP decreases further. At that time a clear distinction can be made between the patients who do and those who do not "respond" with a BP drop. The non responders tend to remain in a salt and fluid depleted state with a renin dependent BP, while in the responders the initially induced hemodynamic changes have largely, but not completely, disappeared.

Blood Pressure↗
PubMed1979

Measurement of cardiac output by impedance cardiography under various conditions.

The suitability of impedance cardiography as a method to follow changes in cardiac output (CO) was investigated by comparing it with thermodilution and by measurements in conditions with predictable effects on CO. The correlation between absolute CO values obtained by impedance and thermodilution techniques was moderate (r = 0.61), but the percentage changes showed a good correlation (r = 0.84). Head-up tilting decreased CO by 25% in 5 normal subjects. Bloodletting in three subjects caused a 20% decrease, reinfusion in one subject a 16% increase. Occlusion of artificial large flow arteriovenous shunts in 6 dialysis patients caused a 12% decrease in CO, whereas the effect was less with moderate and absent with small flow shunts. Ultrafiltration caused a 28% decrease in two dialysis patients. In 20 hypertensive patients CO dropped 25% after salt depletion; propranolol administered intravenously gave a 15% decrease (n = 13), diazoxide intravenously a 30% increase (n = 6). It is concluded that, provided conditions are strictly defined, impedance cardiography is a reproducible method and suitable for the measurement of intrapatient changes in cardiac output.

Adult↗