Determination of nutrient salts by automatic methods both in seawater and brackish water: the phosphate blank

9 páginas, 2 tablas, 2 figurasThe main inconvenience in determining nutrients in seawater by automatic methods is simply solved: the preparation of a suitable blank which corrects the effect of the refractive index change on the recorded signal. Two procedures are proposed, one physical (a simple equation to estimate the effect) and the other chemical (removal of the dissolved phosphorus with ferric hydroxide).Support for this work came from CICYT (MAR88-0245 project) and Conselleria de Pesca de la Xunta de GaliciaPeer reviewe

Studies of the factors modulating antidiuretic hormone excretion in man in response to the osmolar stimulus: effects of oestrogen and angiotensin II

The aim of this study was to assess the influence of hormones known to regulate fluid and electrolyte balance on the release of antidiuretic hormone induced by raising serum osmolality. The stimulus provoked by the infusion of a 2.5% NaCl solution induces an increase of urinary [arginine-8]-vasopressin from 1.12 to 2.64 ng/h in men and from 1.65 to 7.27 ng/h in women as has been previously reported. These results were compared to those obtained in males infused with angiotensin II (AII) before and during a hypertonic sodium load and in males infused with hypertonic saline on the fourth day of administration of ethinyl-oestradiol. During the combined infusion of AII and then hypertonic saline, the mean hourly urinary excretion of AVP increased from 2.8 to 5.67 ng/h. Within each group the increase of urinary AVP was highly significant. The rise of urinary AVP during AII infusion was significantly different from the rise observed both in untreated males and untreated females, lying in between. The mean hourly excretion rate of AVP increased before and after hypertonic saline loading from 2.65 to 5.3 ng/h in males pre-treated with ethinyl-oestradiol. The significant difference observed between males and females is reduced when males treated with oestrogen were compared to female subjects. In each group plasma renin activity decreased to low values during the salt-loading test. During oestrogen treatment PRA and plasma renin substrate rose, while urinary aldosterone remained almost unchanged.(ABSTRACT TRUNCATED AT 250 WORDS

Radioimmunoassay of (8-arginine)-vasopressin. II. Application to determination of antidiuretic hormone in urine

A radioimmunoassay for [8-arginine]-vasopressin (AVP), previously described (Czernichow et al. 1975) has been used for the determination of antidiuretic hormone in a 4 ml urine sample. AVP is extracted from acidified urine with a cation exchanger (Amberlite CG 50) with an overall recovery of 72%. The blank value measured in extracted samples of urine was 0.29 pg/ml +/- 0.21 (SEM) and calculated by extrapolation of the regression line of the recovery experiment was 0.49 pg/ml. The coefficient of variation within-assay was 13% and between-assay 18%. Addition of the amounts of AVP found in each specimen of urine voided gave results nearly identical to those of the amounts found in 24 h pool of urine, indicating that the assay was not affected by changes in concentration of the other urinary components during the day. The daily urinary excretion of AVP measured in 34 subjects was found to be 34 ng in 17 women and 70 ng in 17 men, a significant difference. Urinary concentration and excretion rate of AVP rose during thirst test and during Carter-Robbins test performed in 13 healthy subjects. In the latter test it was observed that the women displayed a strikingly more pronounced AVP elevation after the osmolar stimulus than the men. In both sexes a significant correlation was found between AVP excretion rate and plasma osmolality as well as free water clearance. Three cases of complete or incomplete diabetes insipidus and potomania could be clearly differentiated according to the total output of AVP during the thirst test. Extremely high values of AVP were found in the urine of 5 subjects with Schwartz-Bartter syndrome associated with bronchogenic tumours

Applications cliniques du dosage radioimmunologique de l'hormone antidiuretique [Clinical application of the radioimmunological measurement of the antidiuretic hormone]

A radioimmunoassay specific for arginine-vasopressin (AVP) developed in recent years has been applied to measurement of urinary AVP during physiological and clinical studies. Daily excretion of AVP was 34 +/- 10 ng (mean +/- SD) in 17 female normals and 69 +/- 45 ng in 17 male normals, this being a significant difference (p less than 0.01). After osmolar load (Carter-Robbins test) hourly excretion of AVP increased significantly in 7 males from 1.3 to 3.1 ng/h and in 6 females from 1.7 to 6.5 ng/h. Again the difference between male and female normals was significant. In both sexes a significant correlation between AVP excretion and either plasma osmolality or free-water clearance was found. When the osmolar load test was performed under constant angiotensin II perfusion in male subjects, their AVP excretion was significantly more elevated; this confirmed in man the hypothesis that angiotensin II is a stimulus to AVP secretion. Preliminary results of AVP excretion and response to osmolar load in diabetes insipidus are reported. Exceedingly high rate of excretion of AVP up to 55 330 ng/24 h have been found in cases of bronchial carcinoma with dilutional hyponatremia

Effect on plasma aldosterone, renin activity and cortisol of acute volume depletion induced by ethacrynic acid under constant infusion of angiotensin II and dexamethasone in man

The influence on plasma aldosterone of acute volume depletion induced by ethacrynic acid was studied in man. The experiments were performed during the morning in supine healthy males receiving a control infusion of 5% glucose or an infusion of angiotensin II (AII) to suppress endogenous renin production or an infusion of dexamethasone to suppress endogenous ACTH. Ethacrynic acid induced in all circumstances a similar diuresis and volume depletion. The rise of plasma renin activity (PRA) was effectively suppressed by AII and the rise of plasma cortisol by dexamethasone. Plasma aldosterone (PA) rose markedly even when the elevation of PRA or cortisol were suppressed. Yet when both endogenous renin and ACTH secretion were blocked, PA rose much less after ethacrynic acid. This residual increase could be attributed mainly to a decrease of the metabolic clearance rate (MCR) of aldosterone which had been measured before and after ethacrynic acid administration. The data presented indicate that multiple factors influencing PA after acute volume depletion could be dissected out and that renin, ACTH and a decrease of the MCR each contribute to the elevation of PA