IN VITRO UPTAKE OF TRITIATED SEX STEROIDS BY THE HYPOTHALAMUS OF ADULT MALE RATS TREATED NEONATALLY WITH AN ANTIANDROGEN (CYPROTERONE)

1972 ◽  
Vol 71 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Pentti Tuohimaa ◽  
Mikko Niemi
Keyword(s):  
Cerebral Cortex ◽  
Median Eminence ◽  
Sex Steroids ◽  
Leydig Cells ◽  
Interstitial Cell ◽  
Anterior Hypothalamus ◽  
Male Rats ◽  
Corpora Lutea ◽  
In Vitro Uptake

ABSTRACT Male rats were injected subcutaneously with 2 mg of cyproterone daily from birth to the 14th postnatal day. At the age of 40 days the animals were polycystic and corpora lutea were absent. There was an increased 37% of the ovarian implants showed distinct corpora lutea indicating cyclic secretion of gonadotrophins; the implants in the control animals were polycystic and corpora lutea were absent. There was an increased interstitial cell stimulating hormone output from the pituitary gland as indicated by the increased amount of 3β-hydroxysteroid dehydrogenase active Leydig cells in the testes of the feminized animals. The in vitro uptake of tritiated testosterone and oestradiol of various tissues was tested on rats, age 4.5 months. The anterior hypothalamus, the rostral middle hypothalamus, the median eminence and the anterior pituitary of the feminized males retained significantly more oestradiol than the cerebral cortex. The oestradiol uptake in these areas also exceeded that of the control animals. Only the median eminence of the cyproterone treated rats concentrated more testosterone than the cerebral cortex. The anterior hypothalamus and cerebral cortex of the feminized male rats were less able to transform tritiated testosterone to dihydrotestosterone or tritiated oestradiol to oestrone, as compared to adult castrated male or female animals, respectively.

Improvement of cytochrome P450c17 catalytic processivity as a novel mechanism to attenuate hormonal consequences of enzyme decay in the testes after a gonadotropin surge

1997 ◽  
Vol 136 (4) ◽  
pp. 438-443 ◽  
Author(s):  
W Nikolaus Kühn-Velten
Keyword(s):  
Leydig Cells ◽  
Interstitial Cell ◽  
Cytochrome B5 ◽  
Total Activity ◽  
Male Rats ◽  
Protective Mechanism ◽  
High Dose ◽  
Testosterone Secretion ◽  
Cytochrome P450c17

Abstract Objective: The aim of this study was to gain understanding of the apparent discrepancy between the moderate restriction of testosterone synthesizing capacity and the nearly complete decay of the androgen-producing enzyme, cytochrome P450c17 (CYP17; steroid 17α-hydroxylase/17,20-lyase), in rat testes during the desensitization phase induced by a single, high-dose gonadotropin (human chorionic gonadotropin, hCG) injection. Design and methods: Adult male rats received 25IU hCG i.v., and purified Leydig cells and crude interstitial cell microsomes were prepared 0, 4, 12, 24, 48, 72, 120 and 192 h afterwards. Component CYP17 activities, i.e. simultaneously catalyzed productive androgen formation and abortive 17α-hydroxyprogesterone release, and their ratio (processivity), were compared with CYP17 levels and testosterone secretion rates. Results: Leydig cells isolated 48 h after the artificial hCG surge produce 62% less testosterone than control cells upon stimulation in vitro, though CYP17 levels are reduced by 97%. Its total activity decreases by 87%, resulting in a 4·5-fold rise in the turnover number; the processivity is additionally improved 5-fold over controls. Parallel changes occur in interstitial cell microsomes; a negative linear correlation exists between the ratio of productive over total CYP17 activities and the actual CYP17 concentrations. CYP17 is partly denatured to P420 during hCG action, but other heme proteins (cytochrome b5) remain unchanged. Animal treatment with estradiol results in CYP17 downregulation without any concomitant effect on enzyme processivity. Conclusion: Improved CYP17 processivity is suggested to be the consequence of (otherwise ratelimiting) improved electron transfer efficiency towards CYP17. It explains the relatively high testosterone secretion during Leydig cell desensitization and is interpreted to be a protective mechanism to confine adverse consequences of enzyme decay. European Journal of Endocrinology 136 438–443

IN VITRO UPTAKE OF TRITIATED OESTRADIOL BY THE ANTERIOR HYPOTHALAMUS AND HYPOPHYSIS OF THE RAT

1970 ◽  
Vol 64 (4) ◽  
pp. 687-695 ◽  
Author(s):  
Junzo Kato
Keyword(s):  
Incubation Medium ◽  
Posterior Hypothalamus ◽  
Anterior Hypothalamus ◽  
Ovariectomized Rats ◽  
Free Medium ◽  
Cortex Cerebri ◽  
Anterior Hypophysis ◽  
In Vitro Uptake

ABSTRACT The anterior, middle, and posterior hypothalamus, the cortex cerebri, the anterior hypophysis as well as the diaphragm of adult ovariectomized rats were incubated in vitro with tritiated 17β-oestradiol. The uptake of tritiated oestradiol was differentially distributed intracerebrally with higher accumulation in the anterior hypothalamus and the hypophysis. Lowering the temperature of the incubation medium caused a reduction in the uptake of radioactivity by the anterior hypothalamus as compared to that found in other brain tissues. Tritiated oestradiol taken up in vitro by the anterior hypothalamus and the hypophysis tended to be retained after further incubation in a steroid-free medium. The addition of non-radioactive 17β-oestradiol to the medium inhibited the uptake of tritiated oestradiol by these tissues. Moreover, pretreatment with non-radioactive 17β-oestradiol in vivo prevented the preferential accumulation of tritiated oestradiol in vitro in the anterior hypothalamus and the hypophysis. These results indicate that oestradiol is preferentially taken up in vitro by the anterior hypothalamus and the hypophysis of the rat.

Mechanisms of altered LH secretion in neonatally oestrogenized male rats

1995 ◽  
Vol 147 (1) ◽  
pp. 43-50 ◽  
Author(s):  
L Pinilla ◽  
M Tena-Sempere ◽  
D Gonzalez ◽  
E Aguilar
Keyword(s):  
Leydig Cells ◽  
Postnatal Period ◽  
Male Rats ◽  
Control Groups ◽  
Gonadotrophin Secretion ◽  
Selective Elimination ◽  
Lhrh Release ◽  
Lh Secretion

Abstract It is well known that the control of LH secretion depends on the steroid milieu during the postnatal period. In this study LH secretion was analysed in adult male rats injected neonatally with 500 μg oestradiol benzoate (1) after orchidectomy, (2) after selective elimination of androgens by destruction of Leydig cells with ethylene dimethane sulphonate (EDS), and (3) after removal in orchidectomized animals of Silastic capsules containing testosterone. In addition, (4) in vivo and in vitro LH secretion in response to LHRH agonist and antagonists, (5) the hypothalamic LHRH content, (6) the basal and stimulated in vitro LHRH release, and (7) the LH responses after administration of naloxone (2 mg/kg), α-methyl-p-tyrosine (α-MPT; 250 mg/kg), N-methyl-d-aspartic acid (NMDA, 15 mg/kg) or kainic acid (KA; 15 mg/kg) were also examined. Our data indicated that (1) the LH response after orchidectomy, after EDS administration and after removal of Silastic capsules containing testosterone was diminished in oestrogenized male rats, (2) the pituitaries from oestrogenized males retained responsiveness to LHRH, (3) hypothalamic LHRH content was reduced in oestrogenized males, but the hypothalamus from oestrogenized males released more LHRH than those of control groups both under basal conditions or after depolarization, (4) α-MPT decreased LH secretion only in oestrogenized males, and (5) NMDA and KA stimulated LH only in oestrogenized males. We conclude that in oestrogenized male rats the loss of sensitivity to the negative feedback action of testosterone on LH secretion was not due to decreased pituitary responsiveness to LHRH stimulation or to the inherent damage of LHRH neurones. In contrast, changes in the mechanisms governing LHRH release seem to be involved. A lack of activation of the excitatory noradrenergic and aminoacidergic systems seems to be part of the neurochemical basis of altered gonadotrophin secretion in neonatally oestrogenized male rats. Journal of Endocrinology (1995) 147, 43–50

INTERSTITIAL CELL-STIMULATING HORMONERELEASING ACTIVITY OF HYPOTHALAMIC EXTRACTS IN THE DOG

1966 ◽  
Vol 35 (4) ◽  
pp. 401-408 ◽  
Author(s):  
K. YAMASHITA
Keyword(s):  
Glutamic Acid ◽  
Aspartic Acid ◽  
Butyric Acid ◽  
Median Eminence ◽  
Interstitial Cell ◽  
Brain Regions ◽  
Anterior Hypothalamus ◽  
Catechol Amines ◽  
Intracarotid Administration

SUMMARY 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.

IN VITRO UPTAKE OF ESTRADIOL BY THE ANTERIOR HYPOTHALAMUS AND HYPOPHYSIS OF THE RAT

1969 ◽  
Vol 61 (1_Suppl) ◽  
pp. S193
Author(s):  
Junzo Kato ◽  
Machiko Inaba ◽  
Takuro Kobayashi ◽  
Takashi Kobayashi
Keyword(s):  
Anterior Hypothalamus ◽  
In Vitro Uptake

SYNTHESIS OF ANDROGENS IN VITRO BY TESTES OF RATS ACCLIMATIZED TO A HOT ENVIRONMENT

1971 ◽  
Vol 51 (3) ◽  
pp. 489-498 ◽  
Author(s):  
E. BEDRAK ◽  
V. SAMOILOFF ◽  
U. A. SOD-MORIAH ◽  
S. GOLDBERG
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Oxygen Uptake ◽  
Leydig Cells ◽  
Environmental Temperature ◽  
High Ambient Temperature ◽  
Male Rats ◽  
Similar Degree ◽  
Hot Environment

SUMMARY The relative activities of enzymes participating in the biosynthesis of testosterone via the 4-ene pathway were determined in testicular homogenates of rats acclimatized to a hot environment (33–35 °C, 25–40% relative humidity). Acclimatized animals showed an increase in activity of 17α-hydroxylase, 17,20-lyase and 20α-hydroxysteroid oxidoreductase, whereas the activity of 17β-hydroxysteroid oxidoreductase was markedly decreased. Histological examination of the testes disclosed that neither the germinal epithelium nor the Leydig cells were adversely affected by the increased environmental temperature. The results are discussed in relation to the synthesis and release of the gonadotrophins. A similar degree of acclimatization, as determined by the comparable decrease in oxygen uptake, was achieved by either of two methods: daily 4 h exposure to a high ambient temperature for 4 weeks or continuous maintenance at 35 °C. The former procedure, however, appeared to be the preferred method for acclimatization of male rats since it did not inhibit growth rate and was free of mortality.

STEROID HORMONE FORMATION BY THE RAT OVARY.

1966 ◽  
Vol 51 (1) ◽  
pp. 131-139 ◽  
Author(s):  
Bernard F. Rice ◽  
Albert Segaloff
Keyword(s):  
Steroid Hormone ◽  
Ovarian Tissue ◽  
Female Rats ◽  
Male Rats ◽  
Corpora Lutea ◽  
Castrate Male ◽  
Rat Ovary ◽  
17 Hydroxyprogesterone ◽  
Hormone Formation

ABSTRACT Ovaries were transplanted to the spleens of castrate male rats. After 120 days, slices of ovarian tissue, composed predominantly of corpora lutea, were incubated in Krebs-Ringer bicarbonate medium containing 50 μc acetate-1-14C. Radioactive steroid formation was assessed quantitatively by reverse isotope dilution. The formation of radioactive progesterone and 20α-hydroxy-pregn-4-en-3-one was established. The formation of radioactive 3β-hydroxy-pregn-5-en-20-one, androst-4-ene-3,17-dione, 17-hydroxyprogesterone, testosterone, oestrone and 17β-oestradiol could not be established. It appears that the corpus luteum of the rat, induced by endogenous gonadotrophins, forms only progestins from acetate-1-14C. Contrary to results previously obtained with ovarian tissue transplanted to female rats, radioactive steroid formation in vitro appeared to be augmented by luteinizing hormone (NIH-LH-S1) added to the incubation flasks. Administration of human chorionic gonadotrophin (200 IU/day) for 5 days prior to autopsy did not enhance acetate-1-14C incorporation in vitro.

THYROTROPHIN RELEASING FACTOR (TRF) IN CEREBROSPINAL FLUID OF THE 3RD VENTRICLE OF RAT

1974 ◽  
Vol 76 (2) ◽  
pp. 209-213 ◽  
Author(s):  
K. M. Knigge ◽  
S. A. Joseph
Keyword(s):  
Cerebrospinal Fluid ◽  
Drinking Water ◽  
Median Eminence ◽  
Cold Exposure ◽  
Male Rats ◽  
Assay Method ◽  
Normal Male ◽  
3Rd Ventricle ◽  
Pooled Samples

ABSTRACT The concentration of TRF in cerebrospinal fluid (CSF) of the 3rd ventricle and content of TRF in median eminence of the rat was examined. CSF (0.3–0.5 μl per animal) was collected from the 3rd ventricle by a microcannula technique and pooled samples from 10–15 animals were examined for TRF using an in vitro pituitary assay method. TRF concentration in 3rd ventricle CSF of normal male rats was 18.5 ± 4.2 pg/μl; median eminence contained 115 ± 12 pg. Cold exposure (4°C) for 16–18 h and thyroxine treatment (2.5 μg/day) for 5 days markedly reduced TRF concentration in CSF and content in the median eminence. Treatment with the anti-thyroid drug methimazole (0.01 % in the drinking water) for 5 days did not notably affect TRF in CSF or median eminence.

ISOLATION OF RAT LEYDIG CELLS BY DENSITY GRADIENT CENTRIFUGATION

1982 ◽  
Vol 92 (2) ◽  
pp. 293-NP ◽  
Author(s):  
J. S. GALE ◽  
J. ST J. WAKEFIELD ◽  
H. C. FORD
Keyword(s):  
Density Gradient ◽  
Binding Sites ◽  
Leydig Cells ◽  
Interstitial Cell ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Collagenase Treatment

A rapid method for preparing Leydig cells from rat testes is described. An interstitial cell suspension, prepared by collagenase treatment of decapsulated testes, was centrifuged for 10 min over a cushion of 60% (v/v) Percoll to remove red blood cells, and then centrifuged for 20 min in a 0–60% linear density gradient of Percoll. Seventy-four per cent of the cells present in that fraction of the gradient comprising 35–50% Percoll were Leydig cells; the yield from each testis was about 1·5 × 106 cells. The Leydig cells appeared viable, excluded Trypan blue, possessed high-affinity binding sites for human chorionic gonadotrophin (hCG) and synthesized increased quantities of testosterone in response to hCG. The cells could be stored overnight in 20% (v/v) glycerol at −20 °C, with only minimal effect on the specific activities of a number of enzymes used as markers of subcellular components. Testosterone production in vitro by the cells after storage for 20 h was greater than that of hCG-stimulated fresh cells and was not further increased by hCG.

Effects of hypoxia on testosterone release in rat Leydig cells

2009 ◽  
Vol 297 (5) ◽  
pp. E1039-E1045 ◽  
Author(s):  
Guey-Shyang Hwang ◽  
Szu-Tah Chen ◽  
Te-Jung Chen ◽  
Shyi-Wu Wang
Keyword(s):  
Calcium Channel ◽  
Adenylyl Cyclase ◽  
Intermittent Hypoxia ◽  
Leydig Cells ◽  
Channel Blocker ◽  
Male Rats ◽  
Plasma Testosterone ◽  
Testosterone Production

The aim of this study was to explore the effect and action mechanisms of intermittent hypoxia on the production of testosterone both in vivo and in vitro. Male rats were housed in a hypoxic chamber (12% O2 + 88% N2, 1.5 l/ml) 8 h/day for 4 days. Normoxic rats were used as control. In an in vivo experiment, hypoxic and normoxic rats were euthanized and the blood samples collected. In the in vitro experiment, the enzymatically dispersed rat Leydig cells were prepared and challenged with forskolin (an adenylyl cyclase activator, 10−4 M), 8-Br-cAMP (a membrane-permeable analog of cAMP, 10−4 M), hCG (0.05 IU), the precursors of the biosynthesis testosterone, including 25-OH-C (10−5 M), pregnenolone (10−7 M), progesterone (10−7 M), 17-OH-progesterone (10−7 M), and androstendione (10−7-10−5 M), nifedipine (L-type Ca2+ channel blocker, 10−6-10−4 M), nimodipine (L-type Ca2+ channel blocker, 10−5 M), tetrandrine (L-type Ca2+ channel blocker, 10−5 M), and NAADP (calcium-signaling messenger causing release of calcium from intracellular stores, 10−6-10−4 M). The concentrations of testosterone in plasma and medium were measured by radioimmunoassay. The level of plasma testosterone in hypoxic rats was higher than that in normoxic rats. Enhanced testosterone production was observed in rat Leydig cells treated with hCG, 8-Br-cAMP, or forskolin in both normoxic and hypoxic conditions. Intermittent hypoxia resulted in a further increase of testosterone production in response to the testosterone precursors. The activity of 17β-hydroxysteroid dehydrogenase was stimulated by the treatment of intermittent hypoxia in vitro. The intermittent hypoxia-induced higher production of testosterone was accompanied with the influx of calcium via L-type calcium channel and the increase of intracellular calcium via the mechanism of calcium mobilization. These results suggested that the intermittent hypoxia stimulated the secretion of testosterone at least in part via stimulatory actions on the activities of adenylyl cyclase, cAMP, L-type calcium channel, and steroidogenic enzymes.

Sign in / Sign up

Export Citation Format

Share Document