It has been postulated that the release of antidiuretic hormone (ADH) is regulated by the changes of plasma tonicity and blood volume. But, in addition to these factors, the changes of arterial blood pressure may participate in the control of its secretion.In order to clarify the role of arterial baroreceptors on the release of ADH, the following experiments were performed on dogs. In the first series of experiments, splectomized dogs were used under chloralose-urethane anesthesia. The animals were bled gradedly from a femoral artery, and the amount of each bleeding was 0.5% body weight. Arterial blood was collected and ADH concentrations in plasma were assayed with Yoshida's method. In these experiments, it was observed that the rises of ADH titers in plasma were highly correlated to the reduction of mean arterial blood pressure. On the besis of these results, eight of the dogs under nembutal anesthesia were used for the next experiment in order to observe the effect of acutely induced hypotension on the ADH release. Sodium nitroprusside with 300 μg/ml concentration was infused intravenously at a rate of 13.8-14.7 μg/kg/min over 0.9-3.0 minutes until a mean arterial blood pressure fell to the 51% initial value. Timed samples of arterial blood were collected and ADH concentrations were also determined. Hypotension induced by infusion of sodium nitroprusside resulted in an increse in plasma ADH concentrations from 18.6±4.7 to 52.71±8.7μU/ml. These rises are statistically highly significant (p<0.005). Four minutes later, the mean arterial blood pressure recovered to almost control levels and the elevated plasma ADH titers decreased significantly to 27.2±9.6 μU/ml (p<0.02). But twelve minutes later, striking rises of plasma ADH concentrations were observed in six of the eight dogs (299±121 μU/ml). The rises were variable in amounts, and so these are statistically not significant (0.05<p<0.1). Compared with the results of the following experiments of hemorrhagic hypotension, it cannot be considered that these rises occurred as a delayed response to hypotension. It was reported that sodium nitroprusside may act directly on vascular smooth muscles and depresses blood pressure. It decomposes gradually in the blood with liberation of cyanogen which inhibit cell respiration. Although there is no direct evidence relevant to this point, massive amounts of ADH released may be stimulated by sodium nitroprusside itself and/or its metabolites. In the third series, the experiments of hemorrhagic hypotension were undertaken under nembutal anesthesia in eight dogs. Animals were bled from a femoral ertery at a speed of 6.7±14.7 ml/kg/min for 1.6-3.8 minutes until a mean arterial blood pressure fell to the same order of magnitude that was induced by sodium nitroprusside infusion. Timed arterial blood samples were drawn and ADH concentrations were also measured. The shed blood was returned immediately via an antecubital vein within four minutes. Hemorrhagic hypotension caused significant increase in plasma ADH concentrations from 19.4±7.9 to 110.3±237.7 μU/ml (p<0.05). Four minutes later, when a mean arterial blood pressure elevated markedly to the level of 146% initial value in response to prompt transfusion of the shed blood, ADH titers in plasma fell significantly to 36.8±8.5 μU/ml (p<0.05) and thereafter progressively returned to the control level. The increment of ADH titers in plasma in response to hemorrhagic hypotension seemed to be somewhat higher than those in response to hypotension induced by sodium nitroprusside infusion (0.1<p<0.2). This tendency can possibly be accounted for by considering that in hemorrhagic hypotension, besides the hypotensive effect, reduction of blood volume additively stimulated the release of ADH.

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It has been attempted to demonstrate the thyrotropin releasing factor (TRF) activity in a substance purified from fragments of bovine anterior hypothalamus and investigate the interaction between TRF and thyroid hormone which controls the release of thyrotropin (TSH) from anterior pituitary gland.
Different doses of TRF were injected intravenously into Swiss-Webster strain male rats (100 gm body weight) pretreated with various doses of L-thryroxine Na (T₄). TRF was also administrated to thyroidectomized rats with or without substitution of T₄. Ten minutes after injection of TRF, blood sample was withdrawn from the jugular vein and the plasma TSH activity was estimated by McKenzie's method with slight modification.
The results obtained were as follows. The onset and duration of the thyroxine inhibition of the TRF-activity was influenced by injected doses of T₄. The rats pretreated with T₄ ranging from 1 to 4μg 4 hours previously showed an increase in plasma TSH (over saline treated rats) after administration of 100 μg TRF, whereas the rats treated with 5, 10 or 30μg T₄ did not show any TSH increase by the same amount of TRF. These inhibitions of TSH release became apparent within 2 hour after administration of 10 μg T₄.
When a dose of 50μg of TRF was administered, plasma TSH increase was not observed in the rat rteated with T₄ ranging from 3μg or more.
On the contrary, 500μg TRF was effective in its thryotropin releasing activity for rats treated with prolonged T₄ administration, whereas 100μg TRF was ineffective under the same condition.
Similar observations were performed in thyroidectomized rats. Two weeks after subtotal thyroidectomy, plasma TSH levels were already high and 100μg TRF could not further increase plasma TSH. In the thyroidectomized rats substituted with T₄ 5 or 10μg daily on the 11, 12 and 13th postoperative days, plasma TSH was suppressed and there was a distinct increase of plasma TSH after injection of 100μg TRF. Contrary to this observation, thyrotropin releasing activity of TRF was quite inhibited in thyroidectomized rats with T₄ treatment (5μg daily) for 7 days.
These data indicate that pictuitary TSH seretion is influenced by two components, one hypothalamic stimulatory factor TRF and the other circulatory inhibiting factor i.e. blood T₄ concentration.
Thus, it is thought that the pituitary TSH secretion is designated on the balance between hypothalamic TRF and blood T₄ concentration.

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The radioimmunoassay of hormones has made a rapid progress in recent years, and various methods for the separation of antibody bound and unbound hormone have been reported.
The enzyme proteolysis method was first utilized for the radioimmunoassay of insulin by M.L. Mitchell et al (1967).
The successful application of enzyme proteolysis method to the radioimmunoassay of human growth hormone (HGH) is reported in the present paper.

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There are many reports on diabetogenic effects of glucocorticoid, such as hyperglycemia and glucosuria, in Cushing's syndrome or in steroid diabetes. In order to understand better the effects of glucocorticoid on serum insulin sufficiently, fasting blood sugar and fasting serum insulin were measured in rabbits before and after treatment with hydrocortisone. Rabbits treated with hydrocortisone were divided into five groups as follows.
1. Rabbits administered intramuscularly with hydrocortisone succinate 20 mg/day for a short term (one week)...Group I.
2. Rabbits administered intramuscularly with hydrocortisone acetate 12.5 mg/day for a short term (one week)...Group II.
3. Rabbits administered intramuscularly with hydrocortisone succinate 10-20 mg/ day for a long term (4 weeks)...Group III.
4. Rabbits administered intramuscularly with hydrocortisone succinate 20 mg/day for a long term (8 weeks)...Group IV.
5. Rabbits administered intramuscularly with hydrocortisone acetate 12.5 mg/day for a long term (5 weeks)...Group V.
To examine glucose tolerance and serum insulin response, glucose tolerance test (0.2 g/kg intra-venous administration) was performed before, after 3 weeks, and 2 months after cessation of treatment with hydrocortisone in rabbits.
Five patients with steroid diabetes were also chosen for the glucose tolerance test (50 g per os administration) for the same purpose.
Blood glucose was measured by Hagedorn-Jensen's method. Serum insulin activities were determined for the same serum sample and at the same time, using the rat diaphragm assay (DILA), the rat epididymal fat pad assay (FILA), and the radioimmuno-assay technique (IRI).
An increase of insulin (IRI, DILA and FILA), but no change of blood sugar were. observed in Group I. and Group III. An increase of insulin (IRI, DILA and FILA) and slight hyperglycemia were observed in Group IV. Both hyperinsulinemia (IRI, DILA and FILA) and hyperglycemia were observed in Group II and Group V.
Glucose loading after treatment of 3 weeks with hydrocortisone succinate 20 mg/day in rabbits showed a slight glucose intolerance, high delayed response in DILA and FILA and high response in IRI. Glucose loading after treatment of 3 weeks with hydrocortisone acetate 12.5 mg/day showed glucose intolerance, high delayed response in DILA, high response in FILA and low response in IRI. When steroid diabetes was found in patients who received glucocorticoid as therapy, high response in DILA, high delayed response in FILA and miscellaneous response in IRI were observed.
These facts mean that glucocorticoid causes hyperglycemia, and a sufficient insulin secretion from pancreas regulates hyperglycemia rapidly. However, both the existence of hyperglycemia and of increased secretion of insulin for a long time caused by glucocorticoid would bring about steroid diabetes even if relatively increased insulin is still present.
Steroid diabetes begins at high insulin response, measured by these methods. But diabetes mellitus even in early cases shows low insulin levels in DILA.
Two months after cessation of treatment of hydrocortisone in rabbits, both glucose intolerance and abnormal insulin response returned to almost normal range. Steroid diabetics are also restored to normal glucose tolerance after cessation of glucocorticoid administration. These two facts indicate that glucose intolerance and abnormal insulin response (IRI, DILA and FILA) caused by steroid administration is temporary in mild cases.

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During the past several years many antidiabetic drugs have been used in the treatment of diabetes mellitus. Tolbutamide, as a first choice of medicine, is most popularly used for mild diabetic subjects. Nowadays, it is undoubted that the hypoglycemic action of this drug depends mainly upon the stimulation of β-cells in pancreas and the secretion of insulin. For the assay of serum insulin, three methods have been most commonly used. But there are considerable discrepancies in the values among them, and these results have different significances respectively.
In this study the effect of tolbutamide on serum insulin response was studied after two months' treatment. Serum insulin levels were checked by using three insulin assays simultaneously : the isolated rat diaphragm assay by observing the increase of glucose uptake (DILA), the isolated rat epididymal fat pad assay using the oxidation of radioactive glucose to carbondioxide (FILA) and the radioimmunoassay (IRI).
After overnight fasting, eight subjects with no diabetic heredity as the control group and thirteen mild untreated diabetic subjects received 50 gm. oral glucose tolerance test (GTT) and 2 gm. oral tolbutamide tolerance test (TTT). Thereafter, diabetic patients were treated with 0.5~2.0 gm/day oral administration of tolbutamide and with a diet of 200~300 gm. carbohydrate daily. After two months' treatment, GTT was again undertaken in these diabetic subjects. Comparing the serum insulin response before and after the treatments the effect of tolbutamide was discussed.
In normal subjects, curves of three insulin values during GTT were almost parallel in good response to blood sugar, reaching their peak at 60 min. and returning to fasting levels within 120 min. Among three insulin values, FILA was constantly the highest, DILA was a little lower and IRI was the lowest.
In diabetic subjects before the treatment, fasting and after glucose loading, DILA was still lower and FILA was higher than those of normal. Fasting IRI was somewhat higher than normal. Each insulin curve showed its peak being delayed to 90 min. and the value at 120 min. did not fall to fasting level.
In normal subjects during TTT, blood sugar levels showed the minimum at 30 min. and returned to fasting levels within 180 min. DILA, FILA and IRI rose in the inverse correlation to blood sugar levels.
In diabetic subjects during TTT, the minimum of blood sugar was seen at 180 min. After tolbutamide loading, DILA was lower and FILA showed higher levels than those of normal but IRI curves had no significant differences compared with those of normal.
After two months of tolbutamide treatment, the value of fasting DILA was increased almost twice and fasting FILA was also elevated. Fasting IRI was somewhat decreased compared with that before the treatment. After glucose loading their peak appeared at 60 min. and returned to fasting levels by 120 min. (180 min. in IRI) Low responsiveness of DILA and hyperresponse of FILA during glucose loading were improved by the treatment. The curves of blood sugar and blood insulin by the three methods showed the tendency to approach those of normal subjects.
The diabetic group before the treatment showed lower DILA, higher FILA and somewhat higher IRI in fatsing. Furthermore, in glucose loading, delayed peak and delayed return to fasting levels were recognized. These findings are characteristic changes in the diabetic insulin pattern.
In this study, high blood sugar levels and high IRI response were decreased and low DILA levels were improved by the long-term treatment of tolbutamide. It is not surprising that IRI response to glucose improved after the treatment, because blood sugar levels had obtained a good control. On this occasion, DILA also ought to be decreased. But DILA which had been lowered, was on the contrary, increased almost twice and approached normal levels. The above result indicates that the “DILA-lowering factor”,

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