Enzyme histochemical changes were observed both light and electron microscopically in the thyroid follicular cells of the rats given either TSH or PTU. One enzyme was peroxidase which plays important roles in the synthesis of thyroid hormones and the other was acid phosphatase, one of many lysosomal enzymes.
Light microscopically the follicular cells of normal rat's thyroid were positive by both enzyme stainings. The follicular cells of rats given TSH singly were strongly positive, and the cells of those administrated PTU for 2 weeks were also strongly positive.
Electron microscopically, the localization of thyroid peroxidase activity was found in the following sites :
(a) the perinuclear cisternae (b) the cisternae of the endoplasmic reticulum (c) Golgi complex (d) some apical vesicles. The changes of peroxidase activity in the follicular cells of rats given TSH singly or PTU continuously were as follows : the perinuclear cisternae, the dilated cisternae of r-ER and many apical vesicles were positive after single TSH administration, and the perinuclear cisternae and the dilated cisternae of r-ER were also positive after prolonged PTU administration. From above observations, it was speculated histo-chemically that the endogenous peroxidase activity in the thyroid follicular cells of the rats was elevated after single TSH or prolonged PTU administration.
In order to compare these histochemical changes with biochemical ones of peroxidase activity, peroxidase activity of the rat's thyroids under the same maniplations were determined by guaiacol assay. The peroxidase activity per thyroid lobes from a rat was significantly increased after prolonged administration of TSH and PTU.

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Serum absolute free thyroxine (AFT₄) and triiodothyronine (AFT₃) were studied in ten patients with subacute thyroiditis, whose total serum T₄ levels were elevated, and these were compared with those of ten patients with untreated hyperthyroidism, whose total T₄ were elevated to the identical level.
The mean value of the basal metabolic rate (BMR) in patients with subacute thyroiditis was 16 ± 14.8% (mean ± SD) and was significantly (P<0.001) lower than that (48.7 ± 15.7%) in hyperthyroidism.
Serum thyroxine binding globulin concentrations measured by RIA were normal and did not differ from those in hyperthyroidism.
Percent free T₄ (%FT₄) and AFT₄ were both elevated in subacute thyroiditis to a comparable degree to those in hyperthyroidism.
Serum total T₃, %FT₃ and AFT₃ were also all elevated, but both total T₃ and AFT₃ were significantly (P<0.05, P<0.05) lower than in hyperthyroidism.
Therefore, both of the ratios of T₄/T₃ and AFT₄/AFT₃ were significantly (P<0.01, P<0.01) lower than they were in hyperthyroidism.
These results indicate that the significantly lower BMR and milder manifestation of toxic symptoms in subacute thyroiditis than in hyperthyroidism might be explained by the high ratios of T₄ /T₃ and AFT₄/AFT₃ as well as the short duration of chemical hyperthyroidism.

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Abnormalities in iodide organification were studied in patients with Hashimoto's thyroiditis.
1) A thiocyanate discharge test was performed in 18 patients with proven Hashimoto's thyroiditis. The per cent discharge of the test was significantly higher in groups with lower level of T₄ (<5.5 μg/dl), RSU (<25.5%) and BMR (<+2.5%), and higher levels of TSH (>10.0μU/ml). The per cent thiocyanate discharge was increased in parallel with the degree of hypothyroidism.
2) The content of thyroidal iodine, protein and thyroglobulin was significantly decreased in 5 euthyroid as well as in the remaining hypothyroid patients with Hashimoto's thyroiditis compared with normal tissue (p<0.05, p<0.01 respectively).
3) In 5 euthyroid patients with Hashimoto's thyroiditis, thyroidal peroxidase (TPO) activity (8.17 ± 1.3 U, mean ± SE) was significantly less than in normal tissue (p<0.01). In 5 hypothyroid patients, TPO activity (27.64 ± 13.8 U) was almost the same as in normal tissue (33.7 ± 5.4). A positive correlation was obtained between TPO activity and serum TSH in ten patients with Hashimoto's thyroiditis (r=0.85, p<0.01).
4) In iodination of thyroglobulin in vitro, the per cent of radioiodine bound to the thyroglobulin was normal in two and increased in one euthyroid patient with Hashimoto's thyroiditis. But it was decreased in two and normal in one hypothyroid patient with Hashimoto's thyroiditis.
Hypothyroidism was present despite normal TPO activity and positive discharge test was frequently observed in hypothyroidism with Hashimoto's thyroiditis. Since the degree of in vitro iodination of thyroglobulin was decreased in hypothyroid patients, structural abnormally of thyroglobulin, produced as a result of some immunologic reaction occuring in Hashimoto's thyroiditis, may be the cause of organification defect and hypothyroidism.

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Secretin is an established stimulator of exocrine pancreatic function and has been reported by some to also stimulate insulin release both in vivo and in vitro. Contrary to these observations with natural porcine secretin, synthetic porcine secretin has been revealed to have no influence on insulin release but does stimulate glucagon release from the isolated perfused rat pancreas. Unphysiologically large doses of synthetic porcine secretin has also been confirmed in in vivo experiments to be capable of stimulating not only glucagon but also insulin secretion from the rat pancreas. Thus, the discrepancies between our previous results with synthetic porcine secretin and those obtained with natural porcine secretin may be due to the differences of the preparations of secretin or to the species differences of the experimental animals, or of the experimental system itself.
The present investigation was undertaken to determine the effect of natural porcine secretin on exocrine and endocrine secretions from the rat pancreas in vivo and in vitro.
Pancreases from Wistar male rats were isolated and perfused according to the technique of Kanno. A Krebs Ringer bicarbonate solution containing 4.6% dextran T-70, 0.25% bovine serum albumin and 50 mg/100 ml glucose was used as a perfusion medium. Commercially available secretin (Secrepan^®; Eisai Co., Ltd., Tokyo, Japan : supplied as lyophilized powder containing 30% pure natural porcine secretin and stabilizer), an inactive placebo of secretin containing cystaine and alanine as stabilizers for natural secretin, and 100% pure natural porcine secretin without stabilizer were used as stimulants of pancreatic exocrine and endocrine secretions.
Overnight-fasted Wistar strain rats were used in the in vivo experiments. The rats were anesthetized with sodium pentobarbital by subcutaneous injection. The body temperature was held at 37°C by a heating pad. One of the following solutions was administered into the jugular vein by a single rapid injection : 1 and 50 U/kg natural porcine secretin (Se-crepan^®), and a comparable dose of the placebo of secretin. Blood samples were collected from the portal vein at -10, 0, 2.5, 5, 10, 30 and 60 min.
Immunoreactive insulin (IRI) was measured by polyethylene glycol radioimmunoassay. Immunoreactive glucagon (IRG) was determined by radioimmunoassay by means of dextran coated charcoal using antiserum 30 K. Rat insulin and porcine glucagon were used as standards in the IRI and IRG assays, respectively.
The lowest secretin concentration causing a significant increase in pancreatic flow rate and amylase output from the isolated perfused rat pancreas was 1 mU/ml. The maximal pancreatic flow rate and amylase output required a secretin concentration of 1 U/ml. Higher concentrations of secretin, however, resulted in lower responses of both pancreatic juice flow and amylase output. Commercial secretin at concentrations of 1 mU/ml to 2 U/ml in the presence of 50 mg/100 ml glucose did not cause an increase in the IRI concentration in the portal effluent above the basal value. Secretin at the concentration of inducing the maximal pancreatic exocrine secretion with 50 mg/100 ml glucose (1 U/ml) was infused for 10 min in the presence of 100 and 150 mg/100 ml glucose to determine whether a threshold level of glucose was required for the insulinotropic action of secretin. Commercial secretin at a concentration of 1 U/ml elicited a significant short-termed increase in the IRI response to 100 and 150 mg/100 ml glucose, while 1 U/ml pure natural porcine secretin with-out stabilizer had no effect on IRI secretion, even when perfused with 100 or 150 mg/100 ml glucose.

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Prostaglandins (PGS) have a wide range of actions on reproductive processes. Data have been reported from several laboratories that PGs are involved in the maturation and release of oocyte.
In order to examine the changes in the production of PGs and steroids in ovulation and the effect of an inhibitor of PG biosynthesis on ovulation, we examined the changes in concentrations of PGs and steroids in peripheral plasma, ovarian vein plasma and follicular fluid during the pre-ovulatory period in prepubertal gilts treated with hCG (6 i.u./kg) 72 hrs after PMS (12 i.u./kg) injection.
The levels of progesterone in peripheral plasma, ovarian vein plasma and follicular fluid increased near ovulation. On the other hand, estradiol-17β and testosterone levels reached maximal values 72 hrs after PMS injection and decreased after hCG injection. The levels of PGF_2α in the ovarian vein began to rise and reached maximal values near ovulation.
The concentrations of PGE₁, PGF_2α and 6 keto PGF_1α in the follicular fluid at 72 hrs after PMS treatment but prior to hCG injection was about 16, <8, 27 pg/follicle respectively. The levels of the three PGs remained relatively constant until 18 hrs after hCG injection and thereafter began to rise and reached maximal values (PGE₁, F_2α, 6 keto PGF_1α : 450,658,188 pg/follicle respectively) as the expected time of ovulation approached. The increase curves of those PGs are as follows : PGE₁ : y=4.41t^1.15 + 16 (γ²=0.89, P<0.005), PGF_2α : y=8.34t^0.99 (γ² =0.85, P<0.005), 6 keto PGF_1α : y=7.16t^0.72 + 27 (γ²=0.87, P< 0.005) (y : pg/follicle, t : hrs after hCG injection).
Superovulation was inhibited by the administration of indomethacin and mefenamic acid at 24 hrs after hCG injection. Follicles of the ovary so treated were kept unruptured and grossly swollen. The levels of progesterone in peripheral plasma and ovarian vein plasma after indomethacin treatment were similar to the controls. Few differences were found in the peripheral plasma levels of progesterone, estradio1-17β, testosterone and 17α OH progesterone between the indomethacin treated and control groups. This was also found to be so with progesterone levels in the ovarian vein plasma.
The present study indicated that PG biosynthesis inhibitors such as indomethacin and mefenamic acid resulted in the inhibition of ovulation without interference with steroid production.

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In the present paper, the authors studied the production and localization of human prolactin from normal human chorionic tissue and decidua in early pregnancy (from the 7th to the 9th week after last menstruation) obtained either by curettage or hysterectomy. Immunohistological investigation by the fluorescent antibody technique using human prolactin specific antiserum prepared by the immunization of rabbits revealed that syncytial trophoblast was a production site of prolactin.
Though prolactin was recognized in compact layers of parietal decidua, it was concerned not with production but solely with deposition in intercellular space which was widened edematously with the existence of a collagen-like substance.
By double staining method of the fluorescent antibody technique, prolactin could be differentiated with both hCG and hPL in syncytial trophoblast.

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We reported previously that estradiol (E₂) administration did not cause any difference in uterine estrogen receptor (ER) levels between immature and castrated-adult rats, whereas it induced a specific thymidine kinase (TK) isozyme in immature rats only. This specific isozyme diminished as the rat grew.
In the present paper, uterine TK activity was studied in rats administered with E₂ at various ages. It was noted that TK activity was significantly increased by E₂ administration at age 10 to 20 days, but TK activity was very low when E₂ was administered at age about 50 days. The estrous cycle began to appear when the rats were around 50 days old.
Despite E₂ administration at age 20 days, TK activity did not increase in the rats pretreated with E₂ dipropionate at age 2 days or with PMS at age 17 days. This result indicated the possibility that the disappearance of E₂-induced TK isozyme was hormone-dependent. On the other hand, TK activity in the rats which were castrated at age 21 days did not increase despite E₂ administration at age 50 days and was similar to that of E₂-administered rats at age 50 days. This result indicated that the disappearance of TK isozyme might be age-dependent, too.
³H-thymidine (5 uCi/g B.Wt.) was injected into the tail vein of immature and castratedadult rats 22 hours after E₂ administration. Each uterus was removed 2 hours after theinjection to prepare for radioautography. No silver grain was observed in any uterine cells in both immature and castrated-adult control rats. Silver grains were clearly found in both endometrial and myometrial cells of immature rat administered with E₂. In castrated-adult rats administered with E₂, silver grains were observed in the endometrial cells only.
It is believed that the specific TK isozyme in E₂ administered immature rats was related to DNA synthesis induced by E₂ administration in the myometrial cells. This TK isozyme disappears as the rat grows. It is likely that the disappearance of this specific TK isozyme is age- and hormone-dependent.

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