Evidence of vasopressin in adenohypophysis: research into its role in corticotrope activity

The presence of vasopressin (VP) in pars distalis of rats and pigs was investigated. Using radioimmunoassay and bioassay of VP, a substance with immunological and biological properties of this hormone was found. This substance was not detected in the adenohypophysis of rats with diabetes insipidus. A partial purification of the VP-like peptide showed that it had the chromatographic and electrophoretic properties of VP. It could be identified with arginine vasopressin (AVP) in the case of the rat and lysine-vasopressin (LVP) in the case of the pig. In the Wistar strain, adrenalectomy induced progressively increasing concentrations of adenohypophysial VP. This increase was significant 15 days after surgery. It could be prevented by treatment with dexamethasone. These results indicate that the presence of VP in the anterior pituitary is related to the regulation of ACTH secretion.

Immunoelectronmicroscopic localization of vasopressin in the rat suprachiasmatic nucleus

The classical areas for arginine-vasopressin (AVP) synthesis are the magnocellular supraoptic (SON) and paraventricular nuclei. More recently AVP was also demonstrated in neurons of the parvocellular suprachiasmatic nucleus (SCN) of the rat. This result was substantiated in the present study by means of immunoelectron microscopy, by subjecting sections to antivasopressin plasma. Conventional electron microscopy revealed dense-core vesicles in the SCN cell bodies and fibres (mean diameter 94.7 +/- 0.9 nm and 84.0 +/- 1.1 nm respectively). These vesicles were infrequent within the cell bodies and could not be accumulated by ethanol administration. Immunoelectron microscopy showed a positive reaction in the cell bodies and fibres within vesicles of 96.7 +/- 1.1 nm and 98.5 +/- 1.1 nm and 98.5 +/- 1.2 nm respectively. By comparison, the cell bodies and fibres of the SON showed immunoreactive granules of 143.0 +/- 1.8 and 147.3 +/- 1.8 nm respectively. The presence in the SCN of AVP in vesicles of different size than those in the SON suggests that synthesis of this substance is indeed occurring within the SCN cells.

Antidiuretic hormone in bronchogenic carcinoma

Immunoactive antidiuretic hormone (ADH) was measured by radioimmunoassay in the plasma, lung tumours and metastatic tumours of nineteen patients with bronchogenic carcinoma. Ten patients had hyponatraemia and carcinoma of the small oat cell type. Plasma ADH measured in nine of these patients ranged from 11--270 pg/ml and was elevated above the normal range (4.6--6.2 pg/ml) in all subjects. ADH-immunoreactive material was detectable in all primary lung tumours (range 9--1080 pg/mg wet weight, n = 7) and metastases (range 5--63 pg/mg wet weight, n = 9) obtained from the hyponatraemic patients. A statistical relationship existed between plasma and tumour ADH concentration in six patients where both measurements were performed. Three patients had small cell carcinomas (two oat cell and one anaplastic) without overt hyponatraemia. ADH-like material was detectable in the lung tumours (18 and 1.1 pg/mg wet weight) and liver metastases (4 and 1.0 pg/mg wet weight) of two patients but not in the third. Four of the remaining patients had squamous cell carcinomas and two had adenocarcinomas. None had hyponatraemia. ADH-like material was undetectable in all lung tumours, metastatic tumours and uninvolved tissue from these patients. ADH extracted from the pituitaries of four patients ranged from 6400--13200 pg/mg wet weight. ADH immunoreactive extracts of six lung tumours and nine metastases (all oat cell) showed the same pattern on elution from a Sephadex G-25 column. A large peak, which made up 65% of the total activity, was eluted in the same position as synthetic arginine vasopressin and contained comparable amounts of immunoreactive and bioactive ADH. Two smaller peaks (8 and 27% of total activity) were eluted in positions of higher molecular weight and contained more immunoreactive than bioactive ADH. In contrast, three of four pituitary extracts showed only a single peak which eluted in the same position as marker vasopressin.

The separation of nonapeptides by reversed-phase high-performance liquid chromatography

The separation properties of five nonapeptides on commercial reversed-phase materials have been investigated and the effects of pH, salt concentration and solvent composition have been studied. With appropriate variation of the pH and salt concentration in the mobile phase, it is possible to resolve all of the peptides investigated and their by-products. Mixtures of water and organic solvents (acetonitrile, dioxan, methanol and n-propanol) have been used. The choice of the organic solvent does not strongly influence the separation pattern. The simplicity, speed and quality of the separations and the favourable detection limits (ca. 30 ng) at 220 nm render this technique suitable to routine quantitative analysis.

Antidiuretic peptide in mammalian choroid plexus

Lyophilized bovine, porcine, and human choroid plexuses contain .02-.09 U of antidiuretic activity per milligram. The antidiuretic factor in bovine choroid plexus was concentrated 100 times by extraction with acetic acid, fractional precipitation with acetone and ethyl ether, gel filtration, and paper chromatography. Resulting choroid plexus fraction IIgammaB2 was eluted from Sephadex G-25 in position corresponding to molecular weight between 750 and 3,500; its antidiuretic activity was destroyed by trypsin, performic acid, and thioglycollic acid, but was not affected by leucine aminopeptidase, carboxypeptidase A or B, or cyanogen bromide. HgammaB2 possesses antidiuretic, pressor, and oxytocic potencies (measured in anesthetized-hydrated rat, anesthetized rat, and isolated rat uterus, respectively) of 1.9, 0.5, and 0.1 U/mg, respectively.

The distribution of vasopressin and oxytocin in the hypothalamoneurohypophysial system of the guinea-pig

1. The ratio of the content of vasopressin to that of oxytocin (V/O ratio) was estimated in the supraoptic nucleus (SON), paraventricular nucleus (PVN) and posterior pituitary gland (PIT) of guinea-pigs.2. Extracts were assayed for antidiuretic activity to estimate vasopressin and for milk-ejecting activity to estimate oxytocin. In assays for milk-ejecting activity, trypsin was used to inactivate vasopressin in the extracts.3. The mean V/O ratios in the SON, PVN and PIT were 28, 8.5 and 7.0 respectively in male guinea-pigs, 6.8, 7.4 and 6.9 in non-lactating females, and 5.1, 3.3 and 6.6 in lactating females.4. The distribution of the hormones within the hypothalamus is discussed in relation to their independent release in response to electrical stimulation of the SON and PVN.

Intra-axonal transport and turnover of neurohypophysial hormones in the rat

1. The specific radioactivities of isotopically pure oxytocin and vasopressin prepared from the neural lobe of the pituitary gland have been measured at various times after an intracisternal injection of [(3)H]tyrosine.2. Radioactive hormone began to appear in the gland 1-2 hr after the injection which suggests an intra-axonal transport velocity of 1-2 mm/hr.3. From 7 days onwards the specific radioactivity of each hormone declined exponentially with the same rate constant and a half-life of about 13 days.4. If the decline in radioactivity can be equated with the release of the hormones, the rates of secretion for the male rat in water balance are 18.7 m-u./day for oxytocin and 28.9 m-u./day for vasopressin.5. Calculation from the secretion rates gave steady-state plasma concentrations of about 3 muu./ml. for each hormone.

The development of a radioimmunoassay for arginine-vasopressin: production of antisera and labelled hormone; separation techniques; specificity and sensitivity of the assay in aqueous solution

A radioimmunoassay for vasopressin was developed using antibodies produced against conjugated and non-conjugated arginine vasopressin. Despite the fact that the vasopressin molecule has only eight amino acids, cross reactivity studies showed that these antibodies were specific for different amino acid sequences.

Labelled hormone of high specific activity (350–800 μCi/μg) was produced by a modification of the chloramine-T method. Unreacted iodide was removed by the batchwise addition of an ion-exchange resin. Other techniques of purification produced no advantage over this simple method.

Several methods of separating antibody-bound and free hormone were studied. All except chromatoelectrophoresis proved satisfactory. Ammonium sulphate or ethanol precipitation of bound hormone was chosen because of simplicity, speed and reproducibility.

The lower limit of detection of the assay was 80 pg arginine vasopressin/ml diluent buffer. Therefore an extraction and concentration procedure is necessary for the measurement of basal circulating levels of the hormone.