Stimulation of L-Cystine-Aminopeptidase Activity by Hormonal Steroids and Steroid Analogs in the Hypothalamus and Other Tissues of the Female Rat

Heil, Hailey; Meltzer, Victor N.; Kühl, H.; Abraham, R.; Taubert, H.‐D.

doi:10.1097/00006254-197110000-00016

Cited by 3 publications

(7 citation statements)

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“…We concentrated our interest on the investigation of the L-cystine aryl¬ amidase which has previously been shown to increase its activity in response to injection of steroid hormones (Heil et al 1971;Bickel et al 1972;Kühl et al 1974e). The enzyme-kinetic investigation of this enzyme system revealed some remarkable properties, e. g. a rather low Michaelis constant which in¬ dicates a high affinity of the enzyme toward its substrate.…”

Section: Discussionmentioning

confidence: 99%

“…The results of experiments recently carried out in our laboratory have indicated that the level of hypothalamic arylamidase activity, and the degree of stimulation which could be achieved by treating the animals with steroids was dependent upon their stage of sexual maturation (Kuhl et al 1974è). The stimulation of hypothalamic enzyme activity by gonadal steroids was also found to follow a sex-specific pattern (Heil et al 1971;Bickel et al 1972).…”

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confidence: 85%

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Inactivation of Luteinizing Hormone Releasing Hormone by Rat Hypothalamic L-Cystine Arylamidase

Kühl

Taubert

1975

Acta Endocrinologica

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The rate of hydrolysis of several aminoacyl-4-nitroanilides by rat hypothalamic arylamidases was investigated. The activity of these enzymes which were mainly found in the 105 000 \m=x\ g supernatant fraction of homogenates of the hypothalamus and other parts of the brain was shown to depend upon the presence of metal ions and free thiol groups, and to be inhibited by puromycin. As previous investigations had shown that Cys\ x=r eq-\ NA is an appropriate substrate for measuring hormone effects on hypothalamic arylamidases, L-cystine arylamidase and its interaction with various peptide hormones were examined in detail. It could conclusively be shown that this enzyme interacts particularly with oligopeptides. Its activity was competitively inhibited by TRF, oxytocin, lysine vasopressin, and LH-RH. It was also shown that the biological activity of LH-RH and its inhibitory effect on the hydrolysis of L-cystine-bis-p-nitroanilide decreased when it was incubated for various periods of time with the 105 000 \ m=x\ g supernatant of rat hypothalamus homogenate.After it had been shown that LH-RH is a small peptide consisting of 10 amino acids (Schally et al 1971), it became obvious that proteolytic enzymes of the hypothalamus could play a role in the release and/or metabolic degradation of this neurohormone. The degradation of synthetic LH-RH by brain tissue was Presented in part at the

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 85%

Inactivation of Luteinizing Hormone Releasing Hormone by Rat Hypothalamic L-Cystine Arylamidase

Kühl

Taubert

1975

Acta Endocrinologica

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“…As has been described previously (Kuhl 8c Taubert 1975), the initial reaction velocity of the hydrolysis of various con¬ centrations of Cys-NA, and its inhibition by various amounts of LH-RH were recorded on a Kintrac VII Spectrophotometer. Previous investigations (Heil et al 1971) demon¬ strated that relatively high doses of oestrogens are required to stimulate the enzyme when given sc (7 pg ethinyloestradiol or 50 pg oestradiol-17/? 6.…”

Section: Effect Of Various Doses Of Lh On Hypothalamic L-cystine Arylmentioning

confidence: 99%

“…The changes in hypothalamic enzyme activity 16 h after the injection of various doses of oestradiol-17/3 into a tail vein of 45 day old intact female rats are depicted in Fig. ministration of 7 µg ethinyloestradiol (Heil et al 1971). The iv administra¬ tion of increasing amounts of oestradiol-17/3 resulted in a nearly linear in¬ crease of arylamidase activity in the hypothalamus, a maximal increase of + 60°/o being reached at a dose of 0.1 pg.…”

Section: Effect Of Various Doses Of Lh On Hypothalamic L-cystine Arylmentioning

confidence: 99%

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Short-Loop Feedback Mechanism of Luteinizing Hormone: Lh Stimulates Hypothalamic L-Cystine Arylamidase to Inactivate Lh-Rh in the Rat Hypothalamus

Kühl

Taubert

1975

Acta Endocrinologica

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The effect of the intravenous administration of several hormones on L\ x=r eq-\ cystine arylamidase in the hypothalamus of the rat was examined. The injection of 10 \g=m\gLH into adult male and female rats was followed within 90 min by an increase of the enzyme activity by 50 %, while infantile animals were not affected. When prepuberal rats were pr e\ x=r eq-\ treated sc with testosterone and oestrogen respectively, the iv injection of LH brought about a rise in hypothalamic arylamidase activity. When ovariectomized rats were tested, no response was seen after LH injection unless the animals had been pre-treated with oestrogen and progesterone. The iv injection of 0.1 \g=m\goestradiol-17\g=b\ into female, and of 0.5 \ g=m\ g testosterone into male intact mature rats also resulted in an increase of hypothalamic enzyme activity. The maximal increase in enzyme activity was seen 16 h after steroid treatment. As it had previously been shown that L-cystine arylamidase inactivates LH-RH, it may be assumed that this enzyme is involved in the short-loop feedback of LH. This assumption is based on the observation that an elevation of plasma LH brings about an activation of the enzyme system, which subsequently leads to increased inactivation of LH-RH in the hypothalamus. This mechanism seems to depend on the presence of certain plasma levels of oestrogen in female, and of testosterone in male animals.Since the presence of LH-RH has not been demonstrated in other parts of the brain (McCann 1970), the following experiments were limited to the hypo¬ thalamus.

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Effect of Neonatally Administered Testosterone and Estradiol on Hypothalamic Arylamidases in the Rat

Merat¹,

Kooshesh²,

Ma³

1980

Horm Metab Res

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The activities of 5 arylamidases were measured in the hypothalamic and cortical region of testosterone and estrogen treated rats as well as of untreated controls. There were no significant differences between the enzyme activities in the two regions. The changes in hypothalamic enzyme activities were always parallel to those of their respective cortical regions. The hypothalamic arylamidases of female rats, treated with 0.1 mg testosterone and sacrificed at 45 days of age, showed the following results at different stages of the estrous cycle: In diestrus, minimal and non-significant differences existed between the hypothalamic enzyme activities of the treated and the control rats. In estrus, the hypothalamic arylamidase activities of Ala, Phe, Tyr and Cys significantly decreased. In proestrus, there were significant decreases in the arylamidase activities of Phe, Tyr and Cys. In the 45 day old treated female in which the vaginal opening had not occurred, the hypothalamic arylamidase activities of Ala, Phe and Glu were significantly elevated. Female rats which had received 1.0 mg testosterone showed a permanent estrus, and at 45 days of age only the Ala-arylamidase activity was seen to increase in these animals. When estrogen (0.1 mg) was given to female rats, a significant decrease in arylamidase activity was seen. The 45 day old male rats neonatally treated with 0.1 mg of testosterone exhibited no significant changes in the arylamidase activity. However, when 1.0 mg of the hormone was administered to the males, the arylamidase activities of Ala and Glu were significantly increased. Male rats treated with estrogen (0.1 mg) showed an increased arylamidase activity.

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Stimulation of L-Cystine-Aminopeptidase Activity by Hormonal Steroids and Steroid Analogs in the Hypothalamus and Other Tissues of the Female Rat

Cited by 3 publications

References 0 publications

Inactivation of Luteinizing Hormone Releasing Hormone by Rat Hypothalamic L-Cystine Arylamidase

Inactivation of Luteinizing Hormone Releasing Hormone by Rat Hypothalamic L-Cystine Arylamidase

Short-Loop Feedback Mechanism of Luteinizing Hormone: Lh Stimulates Hypothalamic L-Cystine Arylamidase to Inactivate Lh-Rh in the Rat Hypothalamus

Effect of Neonatally Administered Testosterone and Estradiol on Hypothalamic Arylamidases in the Rat

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