Response of the hypothalamo-neurohypophyseal axis (AVP system) and the kidney to salt load in young propylthiouracil-treated rats.

The development of the ability of the kidney to concentrate urine was studied in normal and propylthiouracil-treated rats by measuring urinary sodium concentration and osmolarity at different ages. It was shown that the normal animals, but not the PTU-treated ones were able to concentrate urine at 35 days of age. The response of the hypothalamo-neurohypophyseal axis (AVP system) and that of the kidney were investigated in the two categories of animals at 35 days of age by measuring concomitantly the AVP content of the hypothalamus and neurohypophysis, the AVP plasma concentration and the natremia and plasma osmolarity at various intervals after intraperitoneal injection of a 5% NaCl solution. In normal, as well as in PTU-treated rats, salt load did not lead to significant modifications of the hypothalamic AVP content. In comparison with normal rats, the neurohypophysis of the PTU-treated ones released AVP more slowly, but with a similar amplitude. In normal rats, the plasma AVP concentration was already maximal 30 min after salt load and then decreased and returned to the normal value at 2 hrs; at the same time, the natremia and plasma osmolarity also recovered their normal value. In contrast, the plasma AVP concentration as well as the natremia remained high 1 h 30 after salt load in PTU-treated rats. It is concluded that PTU-treated young rat is unable to compensate the salt load in normal delays. Beside the slowing in AVP release by neurohypophysis and decreased AVP plasma level, the responsiveness of the kidney seems to be altered.

Immunochemical detection of vasopressin precursors: artificial processing and quantification along the hypothalamo-hypophysial axis.

A novel immunological approach to the problem of the detection and molar evaluation of vasopressin precursors was taken. First, the specificity of anti-vasopressin antibodies was studied and the hormone antigenic determinant was identified as the sequence Cys-Pro-Arg-Gly-NH2. Then this antigenic determinant, not originally shared by the precursors, was reconstituted by tryptic cleavage followed by chemical fixation of glycinamide. This treatment made quantification of precursors by radioimmunoassay possible at a fmol level in various tissues. In normal rat, precursors were found only in the supraoptic nucleus (192 pmol/mg protein), paraventricular nucleus, median eminence and posterior lobe of the hypophysis. The maturation process was followed by the decrease of the ratio of precursor to hormone from 4-5 to 0.02 along the hypothalamo-hypophysial axis. In Brattleboro rats, genetically deficient in vasopressin, no precursor could be detected over the background level; that ensures the specificity and reliability of this approach.

[Influence of the pars intercerebralis and of median sub-ocellar neurosecretory cells on the concentration of vasopressin-like substance in the ventral nerve cord and haemolymph of Locusta migratoria (Orthoptera). Radioimmunoassay and immunohistology (author's transl)]. / Influence de la pars intercerebralis et des cellules neurosécrétrices sous-ocellaires médianes sur la teneur en substance apparentée à la vasopressine dans la chaîne nerveuse ventrale et l'hemolymphe du criquet migrateur. Etude radio-immunologique et immunohistologique.

1 degree In the migratory locust, electrocoagulation of the neurosecretory cells of the pars intercerebralis increases the rate of water elimination, while electrocoagulation of the median sub-ocellar neurosecretory cells elicits a marked water retention. 2 degrees In the first type of experiment, high concentrations of molecules antigenically close to vasopressin can be measured by RIA in the haemolymph; such molecules are practically undetectable in the blood when median sub-ocellar neurosecretory cells are suppressed. 3 degrees Our data lead us to assume that the vasopressin-like molecules detected in the migratory locust promote water elimination.

Autoimmune alterations in the neurohypophysis of rabbits immunized against vasopressin.

Rabbits immunized against vasopressin developed clinical signs of diabetes insipidus persisting for up to two months after the last boost. Ultrastructural and immunocytochemical studies of the neurohypophysis demonstrated autoimmune alterations: infiltration by immune cells and extracellular deposits of immunoglobulins. No alterations were observed in the hypothalamic nuclei synthesizing vasopressin nor in hormone-target cells of the kidney. Immunization against vasopressin may provide the first example of an autoimmune disease in the hypothalamo-neurohypophysial system.

Evolution of vasopressin levels in the hypothalamo-posthypophysial system of the rat during rehydration following water deprivation. Correlation with ultrastructural aspects in the posterior lobe.

Evolution of the (arginine)-vasopressin (AVP) content of the supraoptic (SON), paraventricular (PVN) and suprachiasmatic nuclei (SchN) and of the posterior lobe of the hypophysis (PLH) has been studied in rats at successive stages of rehydration after 4 days deprivation of drinking water. Particular attention has been focussed on short periods of rehydration. Evolution of the AVP content of the hypothalamo-posthypophysial system (HHS), the blood serum AVP concentration and osmolalities of serum and urine were compared. Variations of the AVP content in the different hypothalamo-hypophysial structures, are parallel. A marked depletion of AVP is observed after 2 and 4 days of dehydration. The AVP content of the PLH and of the hypothalamic nuclei shows two dramatic and short increases 15 min and 3 h after the onset of rehydration; these results are discussed in relation to the known physiological regulation mechanism of the HHS. In the PLH depleted by dehydration, reloading with neurosecretory granules (NSG) begins to be noticeable only after 24 h of rehydration, so that it does not seem to account for elevations of the AVP content occurring earlier. These could be related to a marked increase of the smooth endoplasmic reticulum (SER) network taking place in axons and nerve endings before the NSG reloading.

[Syndrome of inappropriate secretion of vasopressin. Apropos of 3 cases]. / Syndrome de sécrétion inappropriée de vasopressine. A propos de 3 observations.

3 cases of inappropriate vasopressin secretion during one case of anaplastic carcinoma of the lung, one case of carcinoma of the prostate with bony metastases and one case of acute intermittent porphyria are presented. The plasma levels of vasopressin, measured by radioimmunoassay were high. Treatment with demeclocycline was attempted in one case. The clearance of free water was positive but the treatment was poorly tolerated by the digestive tract.

[Simultaneous liberation of vasopressin (ADH) and of neurophysins during nicotine perfusion in man]. / Libération simultanée de vasopressine (A.D.H.) et de neurophysines lors de la perfusion de nicotine chez l'homme.

Using the radioimmunoassay (R.I.A.) for neurophysins (I.R.N.) described in 1969, we demonstrated a concomitant, rapid release of both A.D.H. and I.R.N. within the first minutes (2') of the i.v. infusion of nicotine in 11 patients with normal neuropituitary function and 1 patient suffering from a Schwartz-Bartter syndrome. There is a close relationship (r : 0,82, p less than 0.001) similar to that described by other authors, between peak levels of A.D.H. and I.R.N. in all the patients. Hence, we proved that our R.I.A. system is influenced by nicotine stimulated neurophysins (N.S.N.). The negative results previously published by two of us in 5 normal men could have been due to the length of the period between the beginning of the test and the first blood sampling (30 mn).

[Radioimmunoassay for human plasma 8-arginine-vasopressin (author's transl)]. / Dosages plasmatiques radioimmunologiques de la 8-arginine vasopressine. Réponse à la stimulation par la nicotine

The authors have developed a radioimmunoassay for human plasma vasopressin (AVP) which permits the estimation of antidiuretic hormon (ADH) levels as low as 0,8 pg/ml. The average plasma level of AVP after overnight water restriction was found to be 14,3 pg/ml (sd = 4,4 pg/ml) in normal subjects. They provoked a hypersecretion of ADH by the intravenous injection of 1-2 mg of nicotine. In 11 volunteer normal subjects this stimulation by nicotine provoked ADH hypersecretion which reached a maximum between 2nd and 15th minutes after injection. In 3 cases of diabetes insipidus, nicotine injection did not induce ADH hypersecretion; in 1 case of potomania this response was weak; in 2 cases of syndrome of inappropriate ADH secretion, AVP plasma levels were elevated and the response after nicotine stimulation was exaggerated.

[Release of antidiuretic hormone (ADH) under the influence of gastric distention in the rabbit. Demonstration by radioimmunoassay]. / Libération de l'hormone antidiurétique (ADH) sous l'influence de la distension gastrique chez le lapin. Mise en évidence par dosage radio-immunologique

In this investigation, are studied in rabbits, the effects of gastric distention upon plasma concentration of vasopressin; the arginine-vasopressine is determined by a very sensitive radio-immunologic method. Increases of intragastric ballonet pressure up to 10-20 cmH2O induce significant rise in plasma vasopressin concentrations averaging 21 +/- 3,7 muU/ml (base line 6,25 +/- 2,3 muU/ml). Increase of vasopressin is associated with significantly lowered diuresis. Intravenous injections of nicotine induce similar decrease in urine flow and increase of plasma AVP concentrations up to 12,01 +/- 1,7 muU/ml.