In the previous studies we have shown that endogenous secretin induced by an intraduodenal instillation of 0.1N HCl or 1-phenyl-1-hydroxy-n-pentane is not able to stimulate insulin secretion, but exogenous synthetic secretin stimulates pancreatic a-cells in the rat pancreas perfused with glucose 50mg/dl. Contrary to these findings, many investigators have reported that natural porcine secretin can stimulate insulin secretion in man and in the dog.
However, none of the previous reports have determined plasma secretin levels after an exogenous secretin administration. Thus it was not obvious whether insulin-releasing effect of secretin was physiological or pharmacological. Therefore, the present investigation was undertaken to make clear two questions. One was to evaluate the pancreatic endocrine and exocrine secretions in response to a bolus injection of synthetic secretin in the rat. The other was to compare the secretin levels in the portal vein introduced by the bolus injection with that endogenously released by HCl. We also discussed the endocrine and exocrine secretions in response to synthetic secretin after pretreatment of 1mg per kg B.W. atropine sulphate, since in the in vitro perfused rat pancreas, synthetic secretin did not show a direct effect on the pancreatic β-cell. Wistar strain male rats, weighing from 250g B.W. to 300g B.W. were used after a 15 hr starvation period and were anesthetized by a subcutaneous injection of pentobarbital. Various amounts of synthetic secretin (10ng/kg B.W. to 100μg/kg B.W.) were introduced into the jugular vein by a single injection. The flow rate of pancreatic juice and amylase output were measured at 10 min intervals. Plasma insulin, glucagon and secretin in the portal vein were determined by radioimmunoassay.
Immunoreactive insulin (IRI) secretion rapidly occurred in response to 10μg/kg B.W. synthetic secretin. However, the concentration of immunoreactive secretin (IRS, 28.7 ± 4.1ng/ml) at this time was 80 times heigher than the physiological level (351.5 ± 28.4pg/ml) released by 0.1N HCl. Therefore IRI response stimulated by a bolus injection of synthetic secretin may be due to the pharmacological effect of secretin or to the effect of other factors. In contrast to IRI, immunoreactive glucagon (IRG) increased significantly at the same secretin dose of 10ng/kg B.W. as exocrine secretions did. These endocrine secretions in response to 10μg/kg B.W. secretin were suppressed significantly after the pretreatment of atropine sulphate, whereas exocrine secretions were not changed.
The vagal nerve seems to play a significant role on the effect of synthetic secretin on insulin secretion in in vivo rat experiments since insulin secretion in response to synthetic secretin could not be detected in the perfused rat pancreas without a nervous system.

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The determination of ACTH in plasma has become attainable through the development of the radioimmunoassay (RIA). However, the RIA method has inherent limitations, and the value obtained represents the level of immunoreactive ACTH but not necessarily the level of biologically active ACTH. Therefore, a bioassay of ACTH is still the indispensable method of investigating the pituitary-adrenal axis, physiologically and clinically. Recently Sayers et al. reported a sensitive and accurate bioassay using isolated adrenal cells (IAC). But there were many problems to be solved in the application of their technique in determining plasma ACTH concentrations.
In this investigation, the preparation of IAC (which had an invariable activity), the conditions of incubation in this system, the purification of ACTH from plasma, and the protection of ACTH from its degradation were evaluated in order to improve the bioassay technique. Using this method, the dynamics of plasma ACTH at various states of the rat, dog and human were investigated.
The steroidogenic response to ACTH and DBC-AMP of the cells from rats administrated with dexamethasone was more sensitive than that of cells from intact rats. By preincubating IAC, sensitivity of the cells to ACTH and DBC-AMP increased. Production of corticosteroids (CS) by the IAC from rat and dog adrenals showed the log dose response to any given quantity of ACTH. The minimum effective dose was 4 pg of ^1-24ACTH in rat IAC.
IAC from rats was more sensitive to ACTH than that from dogs because CS production of dog IAC was high even when ACTH was not added.
Digestion with 0.125% of trypsin brought a good recovery of freed cells from dog adrenals which responded well to ACTH. A lima bean trypsin inhibitor was more suitable for preparing IAC than was a soybean trypsin inhibitor. Some BSA contained ACTH activi-ty, which was able to be excluded with QUSO treatment.
The steroidogenic response of IAC was suppressed when incubation was performed with unextracted plasma. It was necessary to extract ACTH from plasma. The use of QUSO absorption of plasma ACTH, with a subsequent aqueous acetone elution and evaporation of the eluate at a high temperature was successful in removing interfering substances. ACTH determination with IAC was carried out using the beaker in which the QUSO eluate was evaporated at 60-70°C. By this extraction procedure, no interfering effects were noted as far as the recovery of a small amount of ACTH was examined in 10 human plasma samples.
Plasma ACTH was stable for 3-5 hours when venepuncture was performed with the addition of Trasylol or EDTA and the blood was stored at 4°C.
Inter-assay (CV : 4.3-17.7%) or intra-assay (9.4-19%) reproducibilities and recovery (87-117%) of this assay system were satisfactory.
With this assay system, it was possible to detect the resting levels of ACTH of the rat, dog and human using 2-4ml of plasma.
Following the administration of acetylcholine in dogs, a good correlation was observed between the height of the peak plasma ACTH and the adrenal 11-OHCS output during 60 minutes. The disappearance rates of endogenous ACTH and exogenous ACTH (porcine ACTH or ^1-24 ACTH) in dogs were 2.8, 2.3 and 1.5 minutes, respectively.
Plasma ACTH concentrations in normal human subjects were 18-169pg/ml at 6 : 00 and 0-78pg/ml at 18 : 00 respectively. The administration of metyrapone or stress during abdominal surgery was followed by an increase in plasma ACTH concentrations. Plasma ACTH concentrations in untreated patient with Addison's disease, ectopic ACTH producing tumors, and adrenogenital syndrome were 2480, 2000 and 430pg/ml, respectively.
Sensitivity, precision and specificity of this asssay system using IAC are excellent, and this bioassay system is applicable for the determination of biologically active ACTH levels in plasma.

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Purpose : Although it is known that prostaglandin (PG) causes the release of gonadotropin and prolactin (PRL) in rats, its site of action has not yet been elucidated. Consequently, we undertook this study to determine the relationship between various limbic nuclei and the release of gonadotropin and PRL due to PGE₂.
Methods : Mature, female, Wister rats were castrated and pretreated 3-5 weeks later with estrogen and progesterone. 72 hrs later the following experiments were carried out.
Expt : Using the Albe-Fessard brain map, 2μg PGE₂ was injected into various intracranial sites with a stereotaxic instrument. 15, 30 and 60 min after the experiment, the rats were sacrificed by decapitation, blood was collected, and the adenohypophysis was excised. Serial sections of the brain were prepared, and the site of injection was confirmed.
The gonadotropin and PRL levels in the blood and pituitary were determined by RIA. Results : 1) Following a medial amygdala (m-AMYG) injection, significant changes in the blood and pituitary levels of these hormones were not seen. 2) 30 min following a medial preoptic area (MPO) injection, a significant increase in blood LH content was found, but no change in FSH or PRL was seen. 3) An injection into the third ventricle (IIIV) resulted in a significant increase in blood gonadotropin and PRL levels 15 min later, which correlated with the decrease in pituitary levels. 4) 15 min following an arcuate nucleus (ARC) injection, blood LH content increased significantly to 238.5 ± 80.2ng/ml (as compared to control values of 30.2 ± 9.8ng/ml), correlating with the decrease in pituitary LH. There was also a significant increase in blood PRL after 15 min and a similar tendency for FSH levels.
From this investigation of PG injections into various limbic sites, it is concluded that the nuclei in the vicinity of the IIIv are involved in gonadotropin and PRL secretion due to PG. The ARC is particularly involved in LH secretion.

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The relationship between morphological changes and enzyme activity of the follicular epithelium of the thyroid was studied in five cases of chronic thyroiditis and one of Graves' disease.
In the type of diffuse thyroiditis with oxyphilic epithelium, most oxyphilic cells were negative by peroxidase and acid phosphatase stainings. The epithelial cells in preserved follicles were weakly positive by both stainings. Under electron microscopy the oxyphilic cells showed characteristic cystic dilatation of the endoplasmic reticulum. In diffuse thyroiditis with varied epithelial changes, the results of enzyme histochemistry were various; the oxyphilic cells were negative by both peroxidase and acid phosphatase stainings, whereas the 'small cell nests' were strongly positive by peroxidase stainings, and the cells of hyperplastic follicles were strongly positive by acid phosphatase stainings. Electron microscopical-ly, those cells which are termed here 'small cell nests' contained numerous mitochondria. From these findings the cell kinetics of the follicular epithelium in chronic thyroiditis were speculated as follows : 1) The oxyphilic cells were in a degenerated state and no functional recovery was expected. 2) The small cell nests were regenerating follicles. 3) The hyperplastic epithelium was in an active state, resembling that of a rat's thyroid given TSH.
In one case of Graves' disease treated with anti-thyroid agents for a long period, the results of enzyme histochemistry were also various; the follicular epithelium with papillary proliferation was strongly positive, that with no papillary proliferation was fairly positive, and the cuboidal oxyphilic epithelium with no follicular pattern was negative by both stainings. The latter two epithelial changes were considered to be due to anti-thyroid agents. It was speculated that the cuboidal oxyphilic epithelium in the treated case of Graves' disease was essentially the same as that in the case of chronic thyroiditis from the view point of enzyme histochemistry.

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SQ 14,225, a potent and specific inhibitor of angiotensin I converting enzyme, has been demonstrated to be an effective antihypertensive agent. Because angiotensin I converting enzyme is identical to kiniase II which degradates kinin, both the blockade of vasoconstrictor, angiotensin II and the accumulation of vasodilator, bradykinin may contribute to the blood-pressure-lowering effect of captopril. Our previous study of captopril revealed that its antihypertensive effect correlates significantly with pre-treatment plasma renin activity (PRA) and blood pressure response to the infusion of angiotensin II antagonist. However, this correlation was significant in acute single doses in one or 2 months of administration but was no longer noticed after 4 months of treatment. This indicates that the blockade of the renin-angiotensin-aldosterone system is the major mechanism for the chronic antihypertensive effect within 2 months of treatment with captopril. The present study is to investigate the changes of the renin-angiotensin-aldosterone system and other hormonal factors to assess the possible involvement of other mechanisms in the long term effectiveness of captopril.
Captopril was administered, alone or in combination with diuretics, to 32 hypertensive patients for 1 to 4 month periods. Twenty-one of these patients had essential 4 renal failure, 2 renal parenchymal, 2 malignant, 1 renovascular hypertension. One had Cushing's syndrome and one had a renin-secreting tumor. The daily dose of captopril ranged from 37.5 to 450 mg per day.
A decrease of mean arterial blood pressure (MBP) of more than 13 mmHg after treatment was considered effective. The mean reduction of the MBP was 16 ± 3 -0 ± 4 (mean S.E.) captopril alone and 25 ± 4 -32 ± 5 mmHg in combination therapy. The combination of captopril with diuretics caused more reduction than captopril alone.
PRA, plasma aldosterone concentration (PAC), 24 hour urinary aldosterone and catecholamine excretion (noradrenaline and adrenaline) urinary kallikrein, serum and urinary electrolytes, and creatinine clearance were compared between responders who had a decrement of MBP which exceeded 13 mmHg and non-responders who did not. Compared to non-responders, responders not only had a higher control PRA and a significant elevation of PRA at one month treatment, but also showed persistent fall of PAC, urinary aldosterone secretion and increased plasma potassium. The reductio, urinary sodium and potassium, serum sodium and endogenous creatinine clearance did not show significant differences either before or after treatment.
These findings together with our previous study suggest that the antihypertensive effect of captopril is related to the pretreatment plasma renin level, and the effectiveness of the long term administration of captopril depends mainly on the blockade of angiotensin II formation. However the possibility of the involvement of other mechanisms cannot be ruled out.

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An organ culture system of a male guinea pig hypothalamo-neurohypophyseal complex (HNC) was established. On day 5 in culture, (Na⁺-K⁺) ATPase activity was 0.83 ± 0.11 mM Pi/mg prot/hr (mean ± SEM) : that is, 67% of that on day 1 in culture. ³H-thymidine incorporated into DNA in the explants of HNC was 1,205 ± 185 cpm/μg DNA. The explants responded to the elevated KC1 medium and the hypertonic solution of sodium chloride with a 470 ± 38% and 298 ± 31% increase in arginine vasopression (AVP) release, respectively. This response was inhibited by the addition of tetrodotoxin to the culture medium.
AVP release from the explants in response to angiotensin II increased significantly in a dose dependent manner. [Sar¹, lle⁸] angiotensin II, however, attenuated the response of the explants to angiotensin II when administered simultaneously with angiotensin II. These results suggest that angiotensin II and its analogue cause the AVP release from the explants in a competitive manner.
The concentrations of AVP in the culture media made hypertonic with sodium chloride, sucrose and mannitol were 298 ± 31% (p<0.01), 251 ± 36% (p<0.01) and 255 ± 59% (p<0.05) of their control values, respectively. The hypertonic solutions of sodium chloride, sucrose and mannitol caused AVP release from the explants in vitro, while the hypertonic solutions of glucose and urea were revealed to be poor osmotic stimuli on AVP release. These results support the concept of osmoreceptors to release AVP from the hypothalamo-neurohypophyseal axis.

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