Unlike cortisol, little is known about the role of corticosterone in man. In this study the effects of exogenous and endogenous ACTH, dexamethasone and metyrapone on the secretion of corticosterone and cortisol in healthy subjects were evaluated. Plasma corticosterone and cortisol levels were measured utilizing the specific radioimmunoassay techniques already reported by this laboratory.
The results were as follows :
1. Following the intramuscular administration of β^1-24ACTH in doses of 0.06, 0.13, 0.25 and 0.5 mg at 0900, plasma corticosterone increased to 3.03, 4.67, 4.96 and 4.68 times (mean) as much as basal levels respectively, whereas plasma cortisol increased to 1.70, 1.79, 2.06 and 2.39 times. The rate of corticosterone secretion was higher than that of cortisol in response to exogenous ACTH, and the secretion of corticosterone was induced more rapidly than that of cortisol.
2. Following the single intravenous administration of regular insulin (0.1 U/kg) at 0900, plasma corticosterone increased to 2.3-6.6 times as much as basal levels, whereas plasma cortisol increased to 1.4 - 3.0 times. Endogenous ACTH stimulated the secretion of corticosterone more effectively than it did that of cortisol.
3. Four hours after the oral administration of dexamethasone in doses of 0.25, 0.5, 1.0 and 2.0 mg at 0900, plasma corticosterone decreased to 36.2, 29.7, 37.3 and 33.2% (mean) of basal levels respectively, whereas plasma cortisol decreased to 28.2, 23.6, 14.0 and 19.5% of basal levels. Plasma corticosterone was markedly suppressed by the administration of a small dose (0.25 mg) as well as by a large dose (2.0 mg) of dexamethasone, but plasma corticosterone revealed weaker suppressibility by dexamethasone than did plasma cortisol.
4. Following the oral administration of metyrapone (750 mg) at 0900, the maximum reduction of their plasma corticosterone levels (2.8-4.6 ng/ml) was obtained at one hour later in six out of eight healthy subjects, and maximum reduction to 4.2 ng/ml was noted at two hours later in one healthy subject. After the metyrapone administration, no reduction in plasma corticosterone was noted in one healthy subject. While plasma cortisol levels decreased markedly at one or two hours after the metyrapone administration in all cases, plasma corticosterone levels in healthy subjects responded more poorly to metyrapone than did plasma cortisol levels.
These results suggest that corticosterone secretion might be controlled by some different mechanism from that of cortisol secretion in man.

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The present study was performed to investigate whether long-term cultured rat pancreatic islets possess a postcultural insulin secretory response to hormones and neurotransmitters in spite of their lack of stimulation during the culture period.
We also investigated the method of maintaining the insulin secretory response of islets cultured in a physiological concentration of glucose.
The tissue culture media were TCM 199 supplemented with 5.5 mM glucose (A medium), 5.5 mM glucose plus 1 mM adenosine (B medium), 16.7 mM glucose (C medium), and 16.7 mM glucose plus 1 mM adenosine (D medium).
Short-term incubation after the culture period of 14 days showed that the islets cultured in B, C and D media maintained the same insulin secretory responsiveness to 8.3 mM glucose and/or 5 μM acetylcholine and also to 1 μM epinephrine as did non-cultured islets. A similar response was found among the islets maintained in B, C and D media. An insulin secretory response to epinephrine and phentolamine was deficient in islets cultured in A medium, whereas it was maintained in those cultured in C medium.
The responsiveness of the islets cultured in C medium to the concomitant stimulation by epinephrine and phentolamine was not different from that of the non-cultured islets.
It was thus concluded that the addition of adenosine in the culture medium containing the physiological concentration of glucose was as effective in maintaining the insulin secretory ability of the islets as was the culture medium containing a high concentration of glucose, and it was suggested that even the pancreatic islets cultured in these media, though separated from the innervation, might preserve acetylcholine and adrenergic receptors similar to freshly isolated islets.
Considering the action of adenosine, the necessity of enhancing ATP and C-AMP concentrations in B cells was also suggested in order to maintain the insulin secretory ability of cultured pancreatic islets.

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The angiotensin II receptor in the rabbit, rat and human adrenal gland and that in the rabbit and rat aorta were studied by using [³H] -angiotensin II ([³H] -AII). The adrenal glands and the aorta of each species were centrifuged at 20,000×g for 30 min, and pellets which contained 95% of binding sites were collected and diluted by a buffer [20 mM Tris-HCl buffer (pH 7.4), 120 mM NaCl, 0.2% BSA, 1 mM EDTA] and used as a membrane fraction. The binding study was done by incubating the membrane fraction and [³H] -AII.
After incubation at 25°C for 30 min, the binding of the membrane fraction and [³H] -AII reached the equilibrium state, and free and bound angiotensin II were separated by 0.45 μm filters. Protein concentration was determined according to the method of Lowry.
The binding sites fulfilled the criteria of the receptor which has organ and structure specificities, high affinity and reversibility. We could thus measure angiotensin II receptor in this study correctly and concisely.
The properties of the angiotensin II receptor were analysed by Scatchard plot.
The number of rabbit adrenal receptors (12833 ± 2115 × 10^-15 mol/mg.protein) (M ± SD) was greater than that of the rat (1780 ± 166 × 10^-15 mol/mg·protein) and that of the human (356 ± 124 × 10^-15mol/mg.protein). But the dissociation constant of all species was the same.
The number of aorta binding sites was less than that of the adrenal in rabbits and rats.But the dissociation constant of rabbits and rats aorta binding sites was quite similar to that of adrenal glands.

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Human peripheral blood lymphocytes were studied with the use of fluoresceinated human thyroglobulin (FITC-Tg) for the presence of cells which bind human FITC-Tg (Tg-BL) and which secrete a thyroglobulin antibody (Tg-SL) by culturing them for 5 days with pokeweed mitogen.
In seven out of fifteen (47%) patients with Hashimoto's thyroiditis, an average of 0.18% of lymphocytes were able to bind FITC-Tg, while only one out of six (17%) patients with Graves' disease was able to bind them. No Tg-BLs were detected in five patients with miscellaneous autoimmune diseases and five normal subjects. Tg-BLs were identified as B lymphocytes by their inability to make rosettes with sheep red blood cells. Tg-SLs were detected in six out of eight (75%) patients with Hashimoto's thyroiditis and two out of five (40%) patients with Graves' disease.
The positive rates of Tg-BL and Tg-SL were fairly well correlated with the thyroglobulin antibody titers.

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A radioreceptor assay (RRA) for human growth hormone, using a 100,000g pellet from late pregnant rabbit liver homogenates, was reported by Tsushima, T. and Friesen, H.G. and applied clinically to the study of serum GH in patients with acromegaly. We studied the serum GH of children with growth disorders with RRA and RIA. The GH receptor used for the RRA was prepared according to the method of Tsushima, T. and Friesen, H.G. Iodination of hGH with ¹²⁵I is commonly performed using the lactoperoxidase method, but in our study it was prepared by the chloramine T method as reported by Tsushima, T. and other authors. The specific activity of the hGH tracer was 40-60 μKi/μg. The GH RRA was performed by the method reported by Sneid, D.S. et al. with slight modification. Under these conditions, the sensitivity of the assay was 1.8 ng/ml. RRA interassay variation was 4.2% at 22 ng/ml of serum GH (RIA). The cross reactivity of human prolactin and TSH in this system was not detected, but that of LER-907 was 5%. The mean RRA/RIA ratio of the contaminated GH in LER-907 was 1.050 ± 0.15. The purified hGH, prolactin, TSH and LER-907 used in these studies were provided by the National Institutes of Arthritis, Metabolism and Digestive Diseases.
Due to the limitation in RRA sensitivity and the difference between RIA and RRA, the quantity of GH in low levels of serum GH (lower than 2 ng/ml) was not studied. The mean RRA/RIA ratio of 8 sera from 6 normal adults was 1.37 ± 0.30, ranging from 0.9 to 1.8. In 15 patients with constitutional dwarfism and 8 patients with delayed adolescence, these ratios were 1.236 ± 0.95, ranging from 0.53 to 2.2, and 1.284 ± 0.308, ranging from 0.7 to 1.63. In 4 patients with cerebral gigantism, which is a syndrome consisting of a nonprogressive neurological disorder with mental retardation, advanced height from birth, and skeletal maturation, this ratio was 1.335 ± 0.412. There did not seem to be an abnormal GH in the circulation, which had a greater biological potency than immunological one in this disorder. Some differences in our results as compared to those previously reported by Sneid, D.S. et al. could be explained by the use of different iodination methods.

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The effects of synthetic secretin on the rate of flow of pancreatic juice, the rate of output of amylase, and the rate of release of immunoreactive insulin (IRI) and immunoreactive glucagon (IRG) were simultaneously investigated in the isolated perfused rat pancrease. In this experimental system, factors other than the direct effect of hormonal stimulus on the pancreas, such as the autonomous nervous system or alteration of blood glucose concentrations, could be eliminated while simultaneously determining pancreatic exocrine and endocrine function.
Pancreases from male Wistar rats, weighing 250 - 300 g and fed ad libitum, were isolated and perfused according to the technique of Kanno. The pancreas was perfused with a Krebs Ringer bicarbonate solution of 4.6% dextran-T 70, 0.25% bovine serum albumin and 50 mg/100 ml glucose, and gassed constantly with a 95% 0₂, 5% CO₂ mixture to achieve pH 7.4. Perfusate was administered into the superior mesenteric and celiac artery via a non-recirculating open circuit. Flow rate was kept at about 2.0 ml/min with the aid of a micro-tubing pump. The total portal effluent was collected in chilled tubes at 60 sec intervals for the measurement of IRI and IRG concentrations.
Synthetic secretin was applied by changing the medium reservoir. When the effect of secretin was studied, a 20-min basal period was followed by a 20-min stimulatory period and then a 20-min recovery period.
To determine whether secretin might require high glucose levels for an insulinotropic action, an infusion of secretin at a concentration of 100 ng/ml was superimposed on 100 and 150 mg/100 ml glucose stimulation.
For measurement of pancreatic exocrine secretions, a calibrated capillary tube was attached to the free end of the pancreatic cannula, which was inserted into the distal end of the common duct at a point shortly before its entrance into the duodenum and tied in place. The proximal end of the bile duct was ligated. Every 10 min the capillary tube was replaced and the flow rate of the pancreatic juice was measured. The sample of juice was diluted with a 6% bovine serum albumin solution, and amylase activity was determined by the chromogenic method with blue-dyed starch polymer. Amylase activity was expressed as Somogyi units/10 min.
IRI was measured by polyethylene glycol radioimmunoassay. IRG was determined by radioimmunoassay with the talc absorption technique. Rat insulin and porcine glucagon were used as standards in IRI and IRG assays, respectively.
No changes of IRI levels in the perfusate were obtained with concentrations of synthetic secretin ranging from 0.01 ng/ml to 2 μg/ml. Secretin had no influence on glucose-induced IRI release when superimposed on 100 or 150 mg/100 ml glucose stimulation. On the other hand, uniphasic IRG release was elicited by synthetic secretin in a dose-related fashion in the presence of 50 mg/100 ml glucose. However, secretin-induced IRG responses were completely abolished in the presence of 100 or 150 mg/100 ml glucose.
Contrary to our observations, most of the previous experiments have shown the insulinotropic effect of secretin but have failed to demonstrate the glucagonotropic effect. Moreover, Santensanio et al. have revealed the suppressive effect of secretin on basal and alanine-stimulated IRG secretion in dogs. The reason for this discrepancy between their results and ours is not apparent. It seems that not only species differences but also the doses and the preparation of secretin used, and the levels of glucose concentration perfusing the pancreas have played a part in the contrasting results.
A dose-response relationship was obtained between synthetic secretin and the peak rates of the flow and output of amylase. Maximal flow rate of the pancreatic juice and amylase output were induced with a dose of secretin at 1 μg/ml.

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Captopril, a potent and orally active converting enzyme inhibitor is believed to exert its hypotensive effect largely through the inhibition of the renin-angiotensin system (RAS). In order to examine the renin dependency of blood pressure (BP) in normal rats and rats with two-kidney Goldblatt hypertension (2KGH), spontaneous hypertension (SH) and DOCA-salt hypertension (DSH), we examined the responses of these animals to prolonged administration of captopril. Two types of studies were done on the hypertensive animals : one was performed in the chronic phase when hypertension was established (chronic phase study), and the other was started in the prehypertensive phase (prevention study). Normal rats were studied with and without captopril treatment. 2KGH rats and SHR in the chronic phase study had no untreated controls and the significances of differences were examined between the BP of the control period and those of the treatment period. In other studies each model had its untreated controls. Each experiment consisted of control, treatment, and recovery periods. Captopril, dissolved in the drinking water at a concentration of 0.5 mg/ml, was given during the treatment period to all animals except the untreated controls. The diet contained 1.3% NaCl by weight. BP, water intake, consumption of captopril, urine volume and the urinary excretion of electrolytes were measured in the normal rats and in the hypertensive rats in the chronic phase study. BP, water intake, and the consumption of captopril were measured in the prevention study. BP was measured using a plethysmographic tail method without anesthesia.
Normal rats consumed a mean of 85 mg/kg/day of captopril and BP fell from a mean control value of 112 ± 2 mmHg (Mean ± SE) to 99 ± 3 mmHg on the second day of the treatment period and remained at about this level thereafter; however, a significant difference of the BP from that of the untreated controls was noted only on the sixth day of the treatment period (p <0.001).
Chronic 2KGH rats consumed a mean of 70 mg/kg/day of captopril 5 months after renal artery constriction and BP decreased progressively from 181 ± 8 mmHg on the last day of the control period to a minimum of 130 ± 5 mmHg on the ninth day of treatment (p < 0.001). While there were considerable fluctuations in BP during the treatment period, it remained substantially less than that of the control period. By the twelfth day of the recovery period the BP had returned to values approximating those of the control period. In the prevention study with 2KGH, captopril was started one day after the constriction of the left renal artery and continued for 20 days. Captopril prevented the development of hypertension during the treatment period. By the fifteenth day of the recovery period there was no significant difference between the BP of these rats and those of their control group.
Established SHR (12 weeks of age) also had a steep fall in BP when they consumed a mean of 67 mg/kg/day of captopril. While their BP fell significantly, it did not reach normotensive levels. The expected BP rise in young SHR (5 weeks of age) was prevented by their consumption of a mean of 68 mg/kg/day of captopril. The significant difference between the BP of these rats and those of their untreated controls disappeared on the seventh day of the recovery period.
Chronic DSH rats had no BP reduction with captopril. DSH was not prevented by captopril even though mean consumption of captopril by these rats was more than 200 mg/ kg/day.
No natriuretic, kaliuretic or diuretic activity of captopril was found in this study.
Both chronic 2KGH and SHR, as well as normal rats had depressor responses to captopril even though sodium intake was not restricted.

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