The activity of lactate dehydrogenase (LDH, E. C. 1. 1.1. 27) is relatively high in the anterior pituitary and all five forms of LDH isoenzymes are demonstrated. The relative proportion of M-containing isozymes is about 80% in the normal controlgroup. Both relative and absolute amounts of M type were increased following thyroidectomy and decreased by L-thyroxine (T4) supplement. Some changes in kinetic properties of the anterior pituitary LDH were observed under these altered circumstances. The production of lactate by the rat anterior pituitary was decreased after thyroidectomy, the most decreased formation of lactate being observed 5 days after operation. The decreased lactate formation was restored to the normal level 72 hrs. after T4 treatment. It has been shown that the rate of lactate formation by the anterior pituitary is not dependent on total LDH activity, nor correlate with the change in the isozyme pattern. The incompatibility between the alteration of the LDH isozyme pattern and that of the pituitary carbohydrate metabolism in various thyroid states is discussed.

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Enhancing effect of neutral phosphate on the hypocalcemic response to thyrocalcitonin (TC) has been previously demonstrated in rats. The possibility of in vivo pyrophosphate enhancement of TC effect was investigated in the present study. Marked dose-dependent hypocalcemia was found 60 min. after s.c. injection of graded doses of pyrophosphate (4-1, 024μmols) in both intact and thyroparathyroidectomized rats. At all dose levels of TC used simultaneously injected pyrophosphate markedly enhanced the 60 min, hypocalcemic response to graded doses of TC.

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Acute, subacute and chronic changes in the adrenal of unilaterally adrenalectomized rats were investigated by means of histological observations as well as measuring the adrenal weights and cholesterol contents. The adrenal weights increased after the third postoperative day. The cholesterol concentrations declined gradually in the first 6 hrs., then temporarily recovered in 3 days and again dropped in 7 days. Acute histological changes were induced in one hr. after the operation, and evolutionary arrangements of vertical cell-columns in the entire cortex were made as early as 60 mins. In a few hrs. after the operation, there developed new, immature glomeruli, “blastema”, which piled up in connective tissues of a thickened capsule and grew in size to be combined with cell-columns of the fasciculata. These pilings and subsequent combinations in subacute and chronic phases seem to result in adrenal compensatory enlargement. Acute definite histological changes were demonstrated to be synchronized by the acute decline of cholesterol concentration ratios.

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In the pituitary homograft or autograft placed under the renal capsule of the rat, mature acidophils were hardly generated. However, in the pituitary implanted in apposition with the adrenal cortex in the adrenalectomized rat, the typical acidophils were differentiated to some extent (approximately 8.4%). The adrenocortical graft showed hyperactivity in terms of loss of fat droplets and elongation of cell-columns of the fasciculata. ¹⁴C-serine uptake by the host pituitary and the pituitary graft indicated that ACTH released from the graft itself acted directly upon the adrenal cortex, and that the secretion of ACTH from the pituitary graft might be regulated by a positive feedback mechanism. When the rat was exposed to a chronic stress of ether anesthesia, acidophils of the pituitary graft increased in number (approximately 15%) in proportion with the augmented ¹⁴C-serine uptake. The frequent occurrence of acidophils was postulated to be a specific phenomenon responsible for the pituitary-adrenal system, because no acidophils were differentiated in the pituitary implanted in apposition with the thyroid. By means of appositional transplantation, the possible secretion of ACTH from acidophils was clarified.

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A role of pituitary on the ovarian estrogen secretion was investigated on the rats hypophysectomized at 1 p.m. in proestrus. The estrogen secretion was minimized within 3hrs. after hypophysectomy. Rat pituitary extract (1 gland e.q.) intravenously injected 2 hrs. after hypophysectomy caused 11 fold increase of estrogen concentration in the ovarian venous blood within 1hr., the extent of which was comparable to that of intact control. Either LH or FSH alone was able to restore the estrogen secretion, and the time required to reach the maximal response was 1hr. for LH and 2hrs. for FSH. In the 1 hr. test, the minimal effective dose for NIH-LH-S₃ and NIH-FSH-S₁ appeared to be less than 0.25 and 2.5μg per rat, respectively. The total activities of the two preparations to produce estrogen appeared to be the same. Under the same conditions, 10 IU of prolactin slightly stimulated the secretion, whereas 20mU of ACTH was quite negative. These results confirmed pituitary gonadotropin dependency of estrogen secretion from the ovary having ripened follicles. It was further demonstrated that the ovary, after completion of ovulatory surge of LH, abolished its reactivity to the pituitary extract containing a sufficient amount of substance (s) in promoting estrogen secretion. An exogenous LH injected at 11 a.m. of proestrus also caused termination of ovarian estrogen secretion with a time lag of 3hrs., the duration of which was equivalent to the interval between the initiation of ovulatory discharge of LH and termination of estrogen secretion in intact rats. Either NIH-FSH-S₄ or NIH-LH-S₁₂ was able to terminate estrogen secretion even at a minute dose as small as 10μg per rat. From these facts, it is considered that both FSH and LH provide a dual effect on ovarian estrogen secretion at the preovulatory stage, promotion and suppression; the former is an acute and direct action of hormones on steroidogenesis and the latter probably a delayed and indirect action of ovulation inducing hormone, the release of which initiates the differentiation of estrogen forming cells towards ovulation unfavorable to estrogen synthesis.

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Process of adrenocortical regeneration after bilateral enucleation was studied morphologically by histological autoradiography and electron microscopy. Results of the autoradiographical study revealed that adrenal enucleation induced a rapid cellular proliferation which was almost completed 20 days after operation. The present autoradiographical findings were in agreement with our previous biochemical results. Changes in size and shape of mitochondria and in mitochondrial cristae in addition to the development of network of smooth-surfaced endoplasmic reticulum were examined during the course of adrenal regeneration electron microscopically. The following morphological manifestation of mitochondrial structure, i. e. a) oval shape, b) enlargement in size, cl vesicular cristae and d) increase in so-called division (or septile structure) of mitochondria, seemed to be closely related to the steroidgenesis of the adrenal gland, as well as the development of the network of smooth-surfaced endoplasmic reticulum.

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Changes of a mitotic rate from fetal life to maturity in the hypothalamus, the anterior pituitary and the ovary of the rat were investigated by 3H-thymidine autoradiography. The labeled index of the hypothalamus of the 10-day old rat was 0.4. The labeled index of the anterior pituitary of the embryo on the 18th day of gestation was 24.2, and those of the 1-and 30-day old rats were 5.1 and 0.16, respectively. Shortly after birth the labeled index of follicular cells of the ovary was 22 and in 30-day old rats just before vaginal opening it was 3.9.

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Release of trichloracetic acid-soluble ¹²⁵I from ¹²⁵I-labeled parathyroid hormone was measured after incubation with carrier parathyroid hormone and enzyme preparation obtained from rat kidney with or without inhibitors for 60 minutes at 38°C in order to evaluate parathyroid hormone hydrolyzing or ¹²⁵I-PTH'ase activity. More ¹²⁵I was released as the amount of enzyme preparation was increased, the time of incubation prolonged, or the amount of carrier parathyroid hormone decreased. Maximum ¹²⁵I releasing activity of rat kidney homogenate was found at pH 8.5, while that of rat kidney supernatant was found at pH 4.5. The former enzyme activity was quite predominant in the kidney, while the latter was also found in the spleen in similar concentration. Rat kidney microsome fraction contained the former most abundantly, while supernatant is the main site of the presence of the latter. The 125 I-releasing activity at pH 8.5 of the EDTA treated rat kidney homogenate was activated by Co⁺⁺ and Fe⁺⁺ and that of acetone powder extract of rat kidney by Co⁺⁺, Mn⁺⁺, Ni⁺⁺, and Fe⁺⁺. ¹²⁵I-PTH'ase activity was definitely inhibited by p-chloromercuribenzoate and mercaptoethanol but scarcely by puromycin, monoiodoacetate, 1-arginine, 1-lysine, tosylphenylalanine chloromethylketone, serotonin, phenylacetate, and 0-phenanthroline.

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The results of the pyrogen test in 23 normal subjects (10males and 13 females) were evaluated for the standardization of the test. Pyrogen was given intravenously in a dosage of 0.005μg/kg of body weight, invariably between 8.00 and 9.00a.m. in consideration of the circadian rhythm of plasma corticoids and also the circadian variation in the responsiveness of the hypothalamic-pituitary axis to pyrogen. The level of plasma 17-OHCS increased from the initial value (a), reached the peak at the second (b) or fourth (c) hour after the pyrogen administration and decreased by the sixth hour (d).(First criterion for normal response). Pyrogen index:(b+c)-(a+d) showed 19.86±6.74μg/dl in control subjects, hence the normal range of 10-30μg/dl for clinical use.(Second criterion). Thirteen patients with general paresis tested in the same manner gave the pyrogen index of 6.59±15.33μg/dl, and 7 of them demonstrated responses which deviated from the normality criteria cited above.

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In order to improve reproducibility of a quantitative hemagglutination inhibition for Human Chorionic Gonadotropin, effects of bovine serum albumin, normal rabbit serum and nonpregnant urine on the sensitivity of this test have been studied. As concentration of BSA in a diluent increases up to 1%, the sensitivity increases proportionally. Effect of 2% NRS is comparable to that of 0.1% BSA. Effect of nonpregnant urine on the sensitivity of the test is varied from one individual to another. mean effect of urine, however, nearly equals that of 0.1% BSA. From the comparison of a direct and a serial dilution method, and of dilution in cool and at temperature, it is suggested that the sensitivity increasing effect of protein could ascribed to its protective action to HCG molecules. The use of protein solution to dissolve standard HCG as well as urine samples is recommended for a quantitative or semi-quantitative assay of HCG in urine.

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Studies were made on the effects of acute and chronic cold exposure on amino acid transport and incorporation into isolated rat anterior pituitary in vitro. Acute exposure of the animals to severe cold (1°C) for 3 or 10hrs. resulted in a slight but statistically significant decrease in α-aminoisobutyric acid uptake and ¹⁴C-alanine incorporation into the anterior pituitary, whereas mild cold exposure (7°C) had no detectable effects both in acute and chronic experiments. These effects of cold exposure were discussed in connection with probable increased secretion of releasing factors from the hypothalamus, of protein hormones from the anterior pituitary, and of hormones from some peripheral endocrine organs, each of which may alter the rate of synthesis of anterior pituitary hormones.

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