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K. YAMASHITA
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SUMMARY

The effect of methylenedianiline on the increased testicular 17-oxosteroid secretion caused by human chorionic gonadotrophin (HCG) was studied in dogs.

A single i.v. administration of 20 i.u. HCG/kg. produced a marked increase in the secretion of testicular 17-oxosteroids. The increase in the secretion occurred within 15 min. after the injection and was sustained during the 4 hr. of observation. At the maximum rate of secretion, an i.v. injection of 25 mg. or 100 mg./kg. of methylenedianiline caused a substantial diminution in testicular 17-oxosteroid secretion. This decrease occurred within 15 min. after the injection; the response was reversible. The effect is believed to be due to a block of androgen biosynthesis in the testis.

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K. YAMASHITA
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The results of a previous study (Yamashita, 1965) indicated that rutin antagonizes the action of progesterone on the endometrium of the rabbit. This was demonstrated by quantitative measurement of endometrial carbonic anhydrase activity (Miyake & Pincus, 1958 b; Yamashita & Kurouji, 1961 a, b). Since rutin is a flavonoid glucoside, it seemed desirable to investigate the antagonistic action of other flavonoid compounds. The following compounds were used: hesperidin (3′,5,7-trihydroxy-4′-methoxyflavanone-7-rutinoside), morin (2′,3,4′,5,7-pentahydroxyflavone) and quercetin (3,3′,4′,5,7-pentahydroxyflavone).

The methods used were identical with those described previously (Kurouji, 1963; Yamashita, 1965). Using a modified Clauberg method (1930), rabbits (weighing approximately 1·5 kg.) were primed with oestrogen and received a standard dose of 2 mg. progesterone; simultaneously one of the test compounds was administered either subcutaneously or orally in logarithmically spaced doses of 0·001–100 mg./animal to groups of five rabbits.

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K. YAMASHITA
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Lutwak-Mann (1955) and Pincus, Miyake, Merrill & Longo (1957) have shown that the carbonic anhydrase activity of the uterine endometrium in rabbits primed with oestrogen is mainly under progestin control. Since the activity increased roughly proportionally to that of proliferative development, determinations of endometrial carbonic anhydrase have been utilized as a quantitative test for progestational activity. In a previous paper (Yamashita & Kurouji, 1961 a), we suggested that certain androgens prevent the activating effect of progesterone on the endometrial carbonic anhydrase. However, Lutwak-Mann (1955) has demonstrated that methyltestosterone itself produces marked increases in the content of uterine carbonic anhydrase. The present observation was made to ascertain whether androgenic steroids affect the activity of endometrial carbonic anhydrase. The following androgens were tested: methyltestosterone, androstenedione, androstanolone, stigmasterol and β-sitosterol.

Immature albino rabbits, weighing approximately 1·5 kg., were used. Clauberg's (1930) method was modified in that the animals were primed with 5 μg.

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K. YAMASHITA
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The effect of hypothalamic extracts on 17-ketosteroid secretion by the testis of the dog was investigated. Stalk-median eminence extracts produced an increased rate of 17-ketosteroid secretion by the testis but extracts of the anterior hypothalamus caused little or no increase in the testicular output. No effect was obtained after the administration of extracts of the pre-optic, posterior hypothalamic and other brain regions. Stalk-median eminence extracts, after boiling, were still active in stimulating the testis though part of the activity was lost. The extracts failed to increase the testicular output of 17-ketosteroids in the hypophysectomized dog and the response is thus considered to be pituitary-dependent. Furthermore, intracarotid administration of acetylcholine, catechol amines, γ-amino-n-butyric acid (GABA), glutamic acid and aspartic acid did not stimulate testicular 17-ketosteroid secretion.

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K. YAMASHITA
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M. MIENO
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ER. YAMASHITA
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The concentrations of 17-oxosteroids in the spermatic venous blood of anaesthetized dogs were used as an index of LH release to assess the effects of arginine-vasotocin on the response of the canine pituitary gland to exogenous luteinizing hormone releasing hormone (LH-RH). When injected into the carotid artery, arginine-vasotocin (1·0 μg/kg body wt) caused no significant alterations in the testicular output of 17-oxosteroids. The administration of LH-RH (5 μg/kg body wt, a standard dose) into the carotid artery produced typical stimulation of testicular 17-oxosteroid secretion. Administration of arginine-vasotocin (0·01, 0·1 or 1·0 μg/kg body wt) into the carotid artery 3 h before the administration of a standard dose of LH-RH inhibited the testicular secretion of 17-oxosteroids normally induced by LH-RH. However, pretreatment with arginine-vasotocin (1·0 μg/kg body wt) did not affect the testicular response to i.v. administration of human chorionic gonadotrophin (5 i.u./kg body wt). These results indicate that in the dog, arginine-vasotocin inhibits the LH-RH-induced release of LH by acting directly on the anterior pituitary gland.

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K. YAMASHITA
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M. MIENO
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ER. YAMASHITA
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Arginine-vasotocin (0·1 or 10 ng/kg body wt) was administered into the carotid artery of anaesthetized immature male dogs 3 h before the administration of a standard dose of luteinizing hormone releasing hormone (LH-RH, 5 μg/kg body wt) into the same vessel. The rate of secretion of 17-oxosteroids by the testes in vivo served as an index of luteinizing hormone (LH) secretion. The administration of LH-RH into the carotid artery of control dogs which had been injected with isotonic saline caused a slight but definite increase in the secretion of testicular 17-oxosteroids. This effect of LH-RH on the testicular secretion of steroids was markedly reduced by pretreatment with arginine-vasotocin. However, the testicular response to the i.v. administration of human chorionic gonadotrophin (5 i.u./kg body wt) was unaffected by pretreatment with arginine-vasotocin (10 ng/kg body wt). These results indicate that in immature male dogs, arginine-vasotocin is able to inhibit the action of LH-RH by acting directly on the anterior pituitary gland.

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K. YAMASHITA
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T. SHIMIZU
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It has been shown that the adrenal cortex gives a diminished secretory response to exogenous corticotrophin (ACTH) 2–3 h after exposure to moderate doses of ionizing radiation (Ungar, Rosenfeld, Dorfman & Pincus, 1955; Shima & Matsuba, 1963). The present paper describes observations made on adult dogs for up to 14 days after X-irradiation of one adrenal gland.

Adult mongrel dogs weighing 10·3–18·5 kg were used. Under sodium pentobarbitone anaesthesia, the left adrenal gland was exposed by the left lumbar route and irradiated with 2000 R of X-rays. The X-ray characteristics were: 180 kV peak, 20 mA, focus—surface distance 37 cm, filtration of 0·5 mm Cu and 0·5 mm Al, and half-value-layer 1·0 mm Cu. Dose-rate to the adrenal gland was approximately 130 R/min. Observations were carried out at 2, 7 and 14 days after irradiation.

On the day of observation, each animal was injected s.c. with 0·1 mg dexamethasone-21-phosphate/kg. One

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K. YAMASHITA
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A. AMANO
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Department of Pathophysiology, Atomic Disease Institute, Nagasaki University School of Medicine, Nagasaki, Japan

(Received 8 December 1976)

Since it has been reported that prostaglandin synthesis occurs in rat (Ellis, Johnson & Hargrove, 1972; Carpenter, 1974) and rabbit testes (Christ & van Dorp, 1972), we have studied the 17-oxosteroid secretory response of the testis to human chorionic gonadotrophin (HCG) in dogs pretreated with aspirin, a potent inhibitor of prostaglandin synthesis (Vane, 1971).

Fourteen male mongrel dogs weighing between 7·8 and 19·8 kg were used. Each animal was anaesthetized by i.v. injection of sodium pentobarbitone (25 mg/kg) and the left spermatic vein was cannulated by the lumbar route (Yamashita, 1966). After spermatic venous cannulation, aspirin (20 or 200 mg/kg) was given with 200 ml distilled water into the stomach through an oesophageal catheter. Controls received 200 ml distilled water only. Three hours after the administration of aspirin, 1 ml 0·9% NaCl solution

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K. YAMASHITA
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M. MIENO
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T. SHIMIZU
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ER. YAMASHITA
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SUMMARY

The effect of prostaglandin E2 (PGE2) on the secretion of adrenaline and noradrenaline by the adrenal gland and the interaction between PGE2 and acetylcholine in the adrenal medulla were examined in anaesthetized dogs. In splanchnicotomized dogs, i.v. injection of PGE2 failed to induce any secretion of catecholamines from the adrenal gland, whereas administration of PGE2 into the lumboadrenal artery resulted in a slight, approximately dose-dependent increase in catecholamine secretion within 2 min of the injection. This effect of PGE2 was unaffected by i.v. administration of atropine. Intravenous administration of acetylcholine 1 min after the administration of PGE2 into the lumboadrenal artery of splanchnicotomized atropine-treated dogs had a markedly greater effect on adrenal catecholamine secretion; the resultant output was about twice that evoked by acetylcholine in the absence of PGE2. The effect was more than additive, since the response to acetylcholine was at least one order of magnitude greater than that to PGE2. This indicates that PGE2 and acetylcholine may act synergistically in the adrenal medulla.

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M. MIENO
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ER. YAMASHITA
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M. IIMORI
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K. YAMASHITA
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Department of Pathophysiology, Atomic Disease Institute, Nagasaki University School of Medicine, Nagasaki 852, Japan

(Received 9 January 1978)

Melatonin has been found to inhibit the response of neonatal rat pituitary tissue to luteinizing hormone releasing hormone (LH-RH) in vitro (Martin & Klein, 1976; Martin, Engel & Klein, 1977). This inhibitory effect of melatonin has been observed previously in the pituitary gland of mature male dogs in vivo (Yamashita, Mieno, Shimizu & Yamashita, 1978), but it is not known whether the inhibition is manifested in immature animals. The response of the pituitary gland of the immature male dog to exogenous LH-RH has therefore been investigated; the rate of secretion of 17-oxosteroids by the testis in vivo was used as an index of LH release (Yamashita, 1966).

Melatonin (Sigma Chemical Co.; 100 μg/kg body weight dissolved in 0·5 ml 1·6% ethanol–isotonic saline solution) was administered into the left carotid artery of immature

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