A STUDY OF THE FIRST EIGHT HOURS IN THE STABILIZATION OF PLASMA TESTOSTERONE CONCENTRATION IN THE HEMICASTRATED RAT

1982 ◽  
Vol 92 (2) ◽  
pp. 225-229 ◽  
Author(s):  
A. I. FRANKEL ◽  
E. J. MOCK
Keyword(s):  
Low Dose ◽  
Male Rat ◽  
Plasma Testosterone ◽  
Blood Collection ◽  
Similar Response ◽  
Luteinizing Hormone Releasing Hormone ◽  
Sham Surgery ◽  
One Step ◽  
Lh Rh ◽  
Single Testis

Plasma levels of testosterone fell within 4 h after hemicastration in the mature male rat, and recovered within 8 h, without a compensatory rise in plasma LH from 5 to 480 min after surgery. Pulsatile release of LH was not observed in any group, suggesting the possibility that its alteration was not stimulating the single testis. Luteinizing hormone releasing hormone (LH-RH) stimulated plasma LH concentration equally in both control and hemicastrated rats, rising more sharply only in sham-hemicastrated rats treated with a low dose of LH-RH. Plasma LH rose significantly at the same time (6 h after surgery) in both castrated (in one step) and hemicastrated rats which were castrated (in two steps). Bilateral denervation of the testis did not affect the response of plasma testosterone after hemicastration. There was a remarkably similar response in both plasma LH and testosterone levels to handling, blood collection, anaesthesia, sham-surgery and hemicastration separately or in combination. It was concluded that the response of testosterone to hemicastration was neither related to early changes in plasma LH levels nor to alterations in the hypothalamo-hypophysial axis.

EFFECT OF ACTIVE IMMUNIZATION TO LUTEINIZING HORMONE RELEASING HORMONE ON SERUM AND PITUITARY GONADOTROPHINS, TESTES AND ACCESSORY SEX ORGANS IN THE MALE RAT

1974 ◽  
Vol 63 (2) ◽  
pp. 399-NP ◽  
Author(s):  
H. M. FRASER ◽  
A. GUNN ◽  
S. L. JEFFCOATE ◽  
DIANE T. HOLLAND
Keyword(s):  
Luteinizing Hormone ◽  
Active Immunization ◽  
Male Rats ◽  
Male Rat ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Accessory Sex Organs ◽  
Gonadotrophin Releasing Hormone ◽  
Low Levels ◽  
Lh Rh

SUMMARY Autoimmunity to luteinizing hormone releasing hormone (LH-RH) in adult male rats, induced by immunization with LH-RH conjugated to bovine serum albumin, resulted in atrophy of the testes and secondary sex organs and aspermatogenesis. Both immunoreactive luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum and the pituitary were reduced to low levels compared with those of control animals. It is suggested that antibodies to LH-RH can inhibit the action of endogenous hormone and that LH-RH is, in fact, the gonadotrophin-releasing hormone in the rat, required for the release of both LH and FSH.

EFFECT OF LUTEINIZING HORMONE RELEASING HORMONE ON PLASMA LEVELS OF LUTEINIZING HORMONE, OESTRADIOL AND TESTOSTERONE IN THE MALE DOG

1976 ◽  
Vol 68 (3) ◽  
pp. 469-474 ◽  
Author(s):  
GWYNETH E. JONES ◽  
KAY BAKER ◽  
DIAN R. FAHMY ◽  
A. R. BOYNS
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Levels ◽  
Plasma Testosterone ◽  
Progressive Decline ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Lh Rh ◽  
Plasma Oestradiol

SUMMARY An injection of luteinizing hormone releasing hormone (LH-RH) increased plasma LH and testosterone concentrations in the male dog, but no significant increase in plasma oestradiol-17β levels was observed. Repeated injections of LH-RH produced an increase in plasma LH levels but there was a progressive decline in the response with each injection. The concentration of plasma testosterone reached a maximum within 40 min of the first injection of LH-RH and remained constant thereafter while plasma oestradiol concentration gradually increased with successive injections of LH-RH.

Uninephrectomy inducing quantitative and qualitative changes in LH isoforms in the male rat

1990 ◽  
Vol 123 (3) ◽  
pp. 365-370 ◽  
Author(s):  
Makoto Ujihara ◽  
Kaoru Nomura ◽  
Shohzoh Toraya ◽  
Hiroshi Demura
Keyword(s):  
Surgical Stress ◽  
Distribution Patterns ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Testosterone ◽  
Selective Synthesis ◽  
Renal Growth ◽  
Prostate Weight ◽  
Sham Surgery ◽  
Qualitative Changes

Abstract. Recent findings that LH stimulates renal growth have prompted us to examine whether LH exercises renotropic effects on the growing kidney following uninephrectomy. Intact (not castrated) male rats were used for sham uninephrectomy to induce surgical stress suppressing plasma LH and testosterone levels. Compared to sham surgery, uninephrectomy caused a transient 240% increase in plasma LH with a transient increase in plasma testosterone (80%) and in prostate weight on day 2. Although pituitary LH content did not change, chromatofocusing of pituitary extract revealed changed distribution patterns among seven LH isoforms, suggesting selective synthesis or secretion of LH isoforms. Castrated rats were then used so that surgical stress did not affect LH. Uninephrectomy caused sustained increases in plasma LH levels (60-110% increase) for up to six days. Three days after uninephrectomy, pituitary LH content increased significantly (30% increase) with a change in chromatofocusing profiles of LH isoforms. Plasma and pituitary FSH levels did not change. In summary, uninephrectomy changed LH isoforms quantitatively and qualitatively. These changes imply a change in gonadotropic and renotropic activities of LH after uninephrectomy.

RESPONSE OF THE PITUITARY-TESTICULAR AXIS TO LUTEINIZING HORMONE-RELEASING HORMONE IN THE IMMATURE MALE RAT

1977 ◽  
Vol 84 (2) ◽  
pp. 254-267 ◽  
Author(s):  
H. Edward Grotjan ◽  
Donald C. Johnson
Keyword(s):  
Luteinizing Hormone ◽  
Control Level ◽  
Serum Testosterone ◽  
Male Rats ◽  
Male Rat ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Immature Male ◽  
Serum Lh ◽  
Lh Rh

ABSTRACT Follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone and androstenedione were measured by radioimmunoassays in the sera of immature male rats treated with luteinizing hormone-releasing hormone (LH-RH). A single dose of 10, 20, 40 or 80 ng of LH-RH produced a prompt increase in serum LH: significant changes in FSH were found only with the two larger doses. Serum testosterone increased to peak levels in 20 to 40 min and returned to control level by 120 min. Changes in androstenedione were temporally similar but smaller in magnitude. Four doses of 20 or 40 ng LH-RH given at 20 min intervals did not increase serum LH or testosterone concentrations above those found with a single injection; FSH was slightly higher after the fourth dose. However, 40 ng LH-RH given every 20 min for 2 h produced a dramatic increase in serum LH and FSH: serum and testicular androgens were also much higher during the second hour. A 2 h stimulation with 80 ng LH-RH given ip at 30 min intervals did not alter the response to the same treatment given 24 h later; i. e., neither the pituitary nor the gonad was primed by previous exposure to increased levels of LH-RH or gonadotrophins. These results suggest that a single pulse of LH-RH produces a predictable response in the animal, but multiple episodic stimuli produce variable responses: testes, on the other hand, produce androgens as long as gonadotrophins are available.

LUTEINIZING HORMONE RELEASE IN ENTIRE AND CASTRATED RAMS FOLLOWING INJECTION OF SYNTHETIC LUTEINIZING HORMONE RELEASING HORMONE, AND EFFECT OF TESTOSTERONE PROPIONATE PRE-TREATMENT

1975 ◽  
Vol 64 (1) ◽  
pp. 7-16 ◽  
Author(s):  
D. B. GALLOWAY ◽  
J. PELLETIER
Keyword(s):  
Luteinizing Hormone ◽  
Peak Level ◽  
Plasma Testosterone ◽  
Total Response ◽  
Short Term ◽  
Luteinizing Hormone Releasing Hormone ◽  
Testosterone Treatment ◽  
Releasing Hormone ◽  
Lh Rh

SUMMARY Plasma luteinizing hormone (LH) levels and LH responses to intravenous administration of 100 μg luteinizing hormone releasing hormone (LH-RH) were studied in entire rams, long-term castrated animals (operation performed six months previously), long-term castrated animals treated with testosterone for the two preceding weeks and short-term castrated animals (castrated 3 h before LH-RH injection). LH was measured by radioimmunoassay in samples taken at 5 or 15 min intervals. Basal LH levels were lower in entire rams (0·9 ng/ml) than in long-term castrated animals (6·0 ng/ml). After LH-RH treatment the LH response was much smaller (peak level 9·6 ng/ml, total response 13·3 ng/ml/1 h) and slower (120 min to peak) in entire than in long-term castrated animals (peak level 61·8 ng/ml, total response 141·2 ng/ml/1 h, 29 min to peak). Testosterone treatment after long-term castration depressed the basal LH level and delayed the peak LH response after LH-RH to values similar to those for entire rams. After short-term castration the response to LH-RH was already as great (peak level 70·1 ng/ml, total response 133·6 ng/ml/1 h) as after long-term castration. The latency to peak LH level (82 min) was intermediate between that for untreated and testosterone-treated long-term castrated animals (130 min). Testosterone treatment was considered to have acted on the hypothalamus to depress basal levels. The results provided evidence for the presence of two inhibitory actions of the testis at the pituitary level in the ram: a qualitative delaying action of testosterone and a quantitative inhibitory action of the testis on LH release after LH-RH injection. The latter may also be related to plasma testosterone levels.

CONCENTRATIONS OF TESTOSTERONE IN NEONATAL MALE RATS SUCKLED NATURALLY AND HAND-FED

1982 ◽  
Vol 92 (3) ◽  
pp. 419-424 ◽  
Author(s):  
P. J. B. ANDERSON ◽  
A. E. FATINIKUN ◽  
A. D. SWIFT
Keyword(s):  
Human Milk ◽  
Plasma Levels ◽  
Male Rats ◽  
Male Rat ◽  
Plasma Testosterone ◽  
Milk Replacer ◽  
Testosterone Concentration ◽  
Rat Pups ◽  
Lh Rh ◽  
Lh Releasing Hormone

Concentrations of testosterone were measured daily in plasma of neonatal male rats from the day of birth for 7 days. It was found that a significant (P <0·001) increase in mean plasma levels of testosterone occurs on day 2 of life, followed by a decrease on day 3. Separation of male rat pups from their mothers on the second day of life for as little as 2 h was associated with a significant (P <0·001) fall in plasma testosterone concentration. Hand-feeding the pups with a proprietary human milk substitute (milk-replacer) from birth until the expected time of the testosterone peak resulted in no increase in plasma levels of testosterone; inclusion of an antiserum to LH-releasing hormone (LH-RH) in the milk-replacer decreased the testosterone levels as did removing any supposed endogenous LH-RH in the milk replacer. Addition of a highly potent analogue of LH-RH, either in the presence or absence of the LH-RH antiserum, to the milk-replacer resulted in mean plasma levels of testosterone similar to those in naturally suckled rats. Rats fed with human milk showed an increase in plasma levels of testosterone. It is concluded that the increase in the plasma testosterone concentration found in male rat pups on the second day of life, which may have an important effect on the organization of the brain, is provoked indirectly by LH-RH ingested during suckling.

EFFECT OF CORTISOL OR ADRENOCORTICOTROPHIN ON RELEASE OF LUTEINIZING HORMONE INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE IN THE DAIRY HEIFER

1982 ◽  
Vol 92 (1) ◽  
pp. 141-146 ◽  
Author(s):  
R. L. MATTERI ◽  
G. P. MOBERG
Keyword(s):  
Luteinizing Hormone ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Dairy Heifers ◽  
Significant Difference ◽  
Significant Depression ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
And Control ◽  
Slight Depression

During treatment with cortisol or ACTH, dairy heifers were given two doses of LH releasing hormone (LH-RH) spaced 1·5 h apart. Serum concentrations of cortisol and LH were monitored during each treatment. Treatment with both ACTH and cortisol raised plasma cortisol levels above the respective saline controls (P<0·001). Neither treatment affected basal LH concentrations. A slight depression in LH response was seen in the cortisol-treated animals after the first LH-RH injection, as shown by a statistically significant depression at three of the sample times. There was no significant difference between treated and control LH values after the second LH-RH administration. Treatment with ACTH resulted in significantly reduced LH values at all sample times after both injections of LH-RH.

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