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.

EFFECTS OF MATING AND INJECTION OF LUTEINIZING HORMONE RELEASING HORMONE ON SERUM LUTEINIZING HORMONE AND TESTOSTERONE CONCENTRATIONS IN RABBITS

1978 ◽  
Vol 76 (3) ◽  
pp. 417-425 ◽  
Author(s):  
C. A. BLAKE ◽  
PATRICIA K. BLAKE ◽  
NANCY K. THORNEYCROFT ◽  
I. H. THORNEYCROFT
Keyword(s):  
Luteinizing Hormone ◽  
Serum Testosterone ◽  
Serum Levels ◽  
Transient Increase ◽  
Marked Rise ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Serum Lh ◽  
Before And After ◽  
Lh Rh

The effects of coitus and injection of luteinizing hormone releasing hormone (LH-RH) on serum concentrations of LH, testosterone and dihydrotestosterone (17β-hydroxy-5α-androstan-3-one; DHT) were tested in male rabbits. Before experimentation, male and female rabbits were housed in individual cages in the same room. Male rabbits were then bled by cardiac puncture before and after placement with female rabbits or intravenous injection of LH-RH. Serum LH, testosterone and DHT were measured by radioimmunoassay. Sexual excitement (sniffing, chasing and mounting), with or without intromission, caused a marked rise in serum testosterone and DHT concentrations in only some of the bucks. These increases were accompanied or preceded by a small, transient increase in serum LH. In the rest of the bucks, sexual excitement with or without intromission had either no effect on serum levels of all three hormones, or only serum testosterone and DHT decreased during the collection period. Similar responses were measured in bucks which were housed in a room without does for 2–4 weeks before experimentation. Injection of 10, 30 or 100 ng or 50 μg LH-RH caused serum LH, testosterone and DHT to rise in all bucks tested, but the magnitude of the rises in serum testosterone and DHT were not related to the magnitude of the LH rise. In both mated and LH-RH-injected bucks, the rises in serum testosterone and DHT were greatest in animals with low initial testosterone and DHT values. Under the conditions of this study, the data suggest that: (1) serum testosterone and DHT rise in only some male rabbits after sexual excitement (with or without intromission), (2) the rises in serum testosterone and DHT are dependent on a small transient increase in serum LH and (3) sexual excitement is less likely to cause release of LH-RH in bucks with raised serum testosterone and DHT concentrations.

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.

SERUM LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE CONCENTRATIONS IN IMMATURE FEMALE RATS TREATED WITH MULTIPLE INJECTIONS AND VARIOUS AMOUNTS OF LUTEINIZING HORMONE RELEASING HORMONE

1975 ◽  
Vol 66 (1) ◽  
pp. 13-20 ◽  
Author(s):  
D. C. JOHNSON ◽  
R. S. MALLAMPATI
Keyword(s):  
Luteinizing Hormone ◽  
Constant Stimulus ◽  
Female Rats ◽  
Intact Female ◽  
Immature Female ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Serum Luteinizing Hormone ◽  
Serum Lh ◽  
Lh Rh

SUMMARY Release of immunoreactive LH and FSH was induced in immature intact female rats by repeated injections of synthetic luteinizing hormone releasing hormone (LH-RH). Altering the dose of LH-RH (5, 10, 20, 50 ng) and the frequency of administration (every 10, 20, 30 or 60 min) over a period of 2 h produced a variety of serum LH and FSH concentrations and ratios. When the dose was a constant 20 ng but the frequency of injections was either 20 or 30 min, a steady state in serum gonadotrophin concentrations was reached within 1 h and the level remained the same during the second hour. When given every 10 min, 20 ng LH-RH produced a much higher concentration of both LH and FSH during the second hour of stimulation. Examination of the gonadotrophin levels after each injection of LH-RH showed that the pituitary response was variable in spite of a constant stimulus.

GONADOTROPHIN RELEASE BY A HIGHLY ACTIVE ANALOGUE OF LUTEINIZING HORMONE RELEASING HORMONE IN RATS IMMUNIZED AGAINST LUTEINIZING HORMONE RELEASING HORMONE

1977 ◽  
Vol 74 (2) ◽  
pp. 291-296 ◽  
Author(s):  
H. M. FRASER ◽  
J. SANDOW
Keyword(s):  
Luteinizing Hormone ◽  
Male Rats ◽  
Tertiary Butyl ◽  
Progressive Decline ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Highly Active ◽  
Normal Rat ◽  
Lh Rh

Immunization against luteinizing hormone releasing hormone (LH-RH) in adult male rats produced a progressive decline in LH and FSH in the circulation to low or non-detectable levels. d-Serine-tertiary-butyl6,des-glycine-NH210 LH-RH ethylamide is an analogue of LH-RH having highly active LH-RH properties in the normal rat. Because it is also immunologically different from LH-RH it can stimulate gonadotrophin release from the anterior pituitary gland of rats immunized against LH-RH without interference from the antibody. The analogue stimulated LH and FSH release in rats 15 weeks after immunization against LH-RH when antibody titre was highest, and after long-term (35 weeks) immunization against LH-RH. d-Serine-tertiary-butyl6,des-glycine-NH210 LH-RH ethylamide and related analogues are therefore potentially useful for reversing the effects of immunization against LH-RH.

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