Male fetal rats were castrated in utero on the 21st day of gestation. Twenty-four hrs after the operation, they were given a subcutaneous injection of 22.5μCi of ³H-leucine. One hr later they were autopsied, and their pituitaries were examined autoradiographica lly by the dipping method. Our experiment showed a significant increase in both leucine uptake and percentage of basophilic cells after the castration. Since the parallel relationship between the uptake of leucine and the biosynthesis of anterior pituitary hormones have been recently elucidated, the significant enhancement of leucine uptake by basophilic cells suggests the increase in production of gonadotrophic hormones by these cells. The increase in percentage of basophilic cells also supports the view of the existence of feedback mechanism between the testis and the hypothalamic-pituitary axis in the fetal rat.

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Changes in serum prolactin levels from day 4 before parturition to 24 hr after it of primiparous Sprague-Dawley rats were investigated by radioimmunoassay. Serum prolactin levels rose on day 0 before parturition (1-6 hr before the beginning of parturition) and declined abruptly immediately after parturition (2-6 min after the end of parturition). Serum prolactin levels increased again thereafter and were maintained at a little higher levels between 4 and 7 hr after parturition than on day 10 of lactation. The levels rose further between 9 and 10 hr after parturition to higher levels than on day 0 before parturition. Serum prolactin levels dropped thereafter and were maintained approximately at the level on day 10 of lactation until 24 hr after parturition. There existed no correlations between either two of the following values; time required for parturition, litter size, serum prolactin levels on day 0 before, at 0 and 24 hr after parturition. The coefficient of variation of serum prolactin value examined at each time was always higher than that on day 10 of lactation.

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Owing to the action of the intratesticular LH release reported in the previous paper (Suzuki et al., 1970), LH content of the rat anterior pituitary implanted into the rat testis rapidly decreased to about 1/100 of the original amount at 25 hr after the implantation. By this time, once highly stimulated testosterone output from the treated testis by the action of released LH, returned to almost the intact level again.
The anterior pituitary of extremely low LH content thus obtained was utilized to see whether LRF induces LH release after promoting de novo synthesis of LH, or not. An ovine LRF preparation was infused for 20 minutes into the testis bearing a pituitary implant from 28 hrs after the pituitary implantation. At the assessment of 2 hrs after the start of infusion, LH content of the implant elevated from nearly zero level to the amount surpassing the pre-implanting level by 40%. And a concommitant maximal increase of testosterone output from the testis bearing the implant was also observed.
At least in the preparation used, it is reasonably concluded that the LRF possesses the dual action of release and synthesis of LH as its primary action.

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Thyroid follicular epithelial cells (E-cells) and parafollicular cells (P-cells) were isolated by a new method from rats pretreated with thyroxine. The dissociated cells were centrifuged on the discontinous gradients of dextran A composed of 8 layers from 5% to 40%. The E-cells were found microscopically to be concentrated in 15% layer, while the P-cells in 25 or 30% layer. Each pellet of two kinds of cells was almost free of contamination by other kind of cells. Only the P-cells were responsible for calcitonin production according to bioassay. Both the isolated E-and P-cells certainly differentiated to reproduce the follicles in the control media-199. The new follicle formation from the isolated E-cells was stimulated by TSH, but not by calcium and iodide. On the other hand, the new follicle formation from the isolated P-cells was also facilitated by calcium, calcium and iodide in combination, or TSH. Especially the combined treatment with calcium and iodide resulted in a remarkable hyperplasia of follicles and the typical hyperfunctional picture with an increase of calcitonin content, but with a negligible ¹³¹I uptake. Calcium, calcium plus iodide and TSH commonly provided the P-cells with the deceptive appearance analogous to the stimulated E-cells. The functions of the both cells were, however, never converted reciprocally during culture under any condition.

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Morphologic and volume changes of the pancreatic islets during perinatal days in the rat were studied.
During 3 days at the end of fetal life, the islet cells containing Gomori's aldehydepositive β granules gradually increased in number and in degree of granulation. The total volume of islets sharply increased at term.
After birth, the total volume of the islets did not increase. The size of islet cells was markedly reduced. The number of β granules in islet cells markedly increased. These observations would support the view of some limitations of insulin secretion under a normal physiologic condition at least during the first 3 days after birth in the rat.

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The effect of castration on the urinary excretion of a gonadotropin-inhibiting substance was studied in male albino rats. Ovulation induced with PMS and HCC was not inhibited in mice which received a heated extract prepared from the urine of castrated rats, while the ovulation was inhibited in mice given a heated extract from the urine of intact rats. This finding indicates that the excretion of a gonadotropin-inhibitor is strongly suppressed in the urine of the rats which are castrated. Administration of testosterone to the castrated rats exerted no effect on the decreased excretion of the inhibitor. The present observations and the results obtained previously suggest that the pituitary and the testes are involved in the secretion of a gonadotropin-inhibitor from the pineal.

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A single injection of non-sedative dose of chlorpromazine hydrochloride (CPZ) on the day of proestrus delayed the spontaneous ovulation by about 24hr in the 4-day cycling rat under the controlled lighting (14L:10D, light on 07:30-21:30). The single doses of CPZ injected subcutaneously from 09: 30 to 16: 30 (or intravenously to 17:30) on the day of proestrus, produced the dose-dependent increase in number of the animals blocked their ovulation. The retardation of injection time during this period increased incidence of the ovulation-blocked rat. At 15:30 and 16: 30, a single subcutaneous dose of 0.15mg CPZ blocked ovulation in all of the rats. After 17:30, the blocking effect of CPZ decreased, and at 20:30, even the sedative dose, 4.8mg did not block ovulation.
Ovulation-inducing effects of various estrogens and progestins were investigated in these CPZ-blocked rats. Incidence peak of ovulation, induced in 45% of the animals, was found at the dose of 64μg estrone, and no ovulation was obtained at the doses either below 8μg or above 512μEg. Estradiol benzoate and Premarin both in a wide range of doses showed the ovulation-inducing effect. Clomiphene citrate in the doses used did not practically induce ovulation. Though the estrogens used except clomiphene citrate were effective, the incidence of induced ovulation were considerably low. On the other hand, progesterone and dydrogesterone were highly effective to evoke the complete ovulatory response in all of the animals. Norethindrone was relatively less effective and testosterone did not induce ovulation.

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The secretory activities of prolactin and GH of the mouse anterior pituitary were determined from ¹⁴C-leucine incorporation in vitro into these hormones. Prolactin and GH of the mouse anterior pituitary were fractionated by disc electrophoresis on polyacrylamide gel.
Neither synthesis nor release of prolactin and GH was different between estrus and diestrus in C3H/He strain of virgin mice. No relation existed between the number of placentae and the pituitary secretory activities of these hormones on day 19 of pregnancy when the number of placentae was adjusted to 1-8 each on day 8. Synthesis of prolactin and GH was significantly higher and percent release of these hormones was lower on day 19 of pregnancy than during virginal stages.

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The effect of buccal administration of oxytocin tablet (100 u) on plasma FFA and TG was studied in healthy subjects. As a result, a decrease of plasma FFA (101±27μEq/1) in the male and an increase (88±34μEq/l) in the female were detected 60min after the administration. Changes of plasma TG also suggested a similar tendency both in males and in females. Thus, sex differences in oxytocin effects on plasma FFA were observed after buccal administration, however the rate of change was rather small compared with the data obtained by intramuscular injection of oxytocin (5 u). The effect of oxytocin administration on plasma FFA was preliminarily investigated in female patients with simple obesity, and an increase of plasma FFA was found to be somewhat higher than in normal females.

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Extra-adrenal action of metyrapone (Metopiron, SU-4885, CIBA) upon HGH and ACTH secretion was investigated in four control subjects and three patients with hypoadrenalism. The administration of metyrapone caused the increase in plasma HGH not only in control subjects but also in three patients with hypoadrenalism. Plasma ACTH levels following the administration of metyrapone increased in a patient with Addison's disease and in an adrenalectomized patient due to Cushing's syndrome. Metyrapone did not cause the significant change in blood sugar levels during the test period. Plasma cortisol levels fell rapidly for 2 hr and reached a plateau and then increased at 4 hr after metyrapone administration in control subjects. In three patients with hypoadrenalism, plasma cortisol levels were low at resting time and became lower to an undetectable level after the administration. All subjects complained of side effects, such as gastric pain, fatigue etc.
These findings demonstrate that there is an extra-adrenal action of metyrapone upon HGH secretion and suggest that metyrapone may stimulate directly the release of ACTH by the pituitary. Its action may not be mediated by glucose metabolism and cortisol metabolism, but may be a direct action on the central nervous system. Our experiment does not make clear whether a direct action of metyrapone on the central nervous system is a specific effect or not.

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Effect of ACTH administration on the rate of phospholipid exchange in vitro between rat adrenal microsomes and mitochondria was examined using ³H-cholinelabeled adrenal microsomes as the donor of phospholipids. Increased rate of exchange was observed between control microsomes and mitochondria isolated from rats received 6 u. of ACTH 3.5 hr before death of the animals. On the contrary, mitochondria obtained from the animals treated with ACTH for consecutive 3 days exhibited less capacity of the exchange. The almost identical results were obtained when the microsomes obtained from ACTH-treated animals were used as the donor of phospholipids. Attempts for the exchange of phospholipid in vitro between inner and outer membranes of adrenal mitochondria and between microsomes and inner membrane of mitochondria were unsuccessful.

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Ovulation was blocked by a single subcutaneous injection of chlorpromazine hydrochloride (CPZ) in the proestrous rat running 4-day estrous cycle under the controlled illumination (14L:10D). Ovulation inducing activities of various progestins including 4 newly synthesized compounds in this institute, were examined in these CPZblocked rats and compared with their endometrial proliferative activities in the rabbit.
Activities of endometrial proliferation in the rabbit, of ovulation induction in the rat, and of pregnancy maintenance in the rat were not always parallel in the progestins assayed.

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