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This study aimed to determine the effect of streptozotocin (STZ)-induced diabetes on pulsatile LH secretion in the mature male rat. LH pulse frequency was reduced by 56% and pulse amplitude by 54%, with a consequential decrease of 72% in mean LH levels 8 days after i.v. administration of STZ (55 mg/kg) to castrated Wistar rats compared with castrated non-diabetic controls. Twice daily insulin treatment completely reversed all parameters of pulsatile LH secretion to control values. Food-restricted non-diabetic controls, studied to distinguish the metabolic effect of diabetes from that of concurrent weight loss, demonstrated a 34% reduction in LH pulse frequency but no significant changes in LH pulse amplitude or mean LH levels compared with non-diabetic controls given free access to food. To distinguish whether the decreased LH pulse amplitude in diabetes was due to a reduction in either the quantity of hypothalamic gonadotrophin-releasing hormone (GnRH) released per secretory episode or to decreased pituitary responsiveness to GnRH, the responsiveness of the pituitary to exogenous GnRH (1-1000 ng/kg body weight) was tested in diabetic rats after castration, using a full Latin square experimental design. The net LH response (total area under response curve over 40 min following GnRH) was decreased by 33% (P = 0.001) in diabetic compared with control rats. The decreased LH pulse frequency in STZ-induced diabetes therefore suggests that the metabolic effect of diabetes is to decelerate directly the firing rate of the hypothalamic GnRH pulse generator independent of testicular feedback. These effects were fully reversed by insulin treatment and were only partly due to the associated weight loss.(ABSTRACT TRUNCATED AT 250 WORDS)
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
May 1981,
Biology of reproduction,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
October 1988,
The Journal of endocrinology,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
January 2000,
Brain research,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
January 1983,
Neuroendocrinology,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
May 2009,
Stress (Amsterdam, Netherlands),
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
April 2001,
Neuroreport,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
January 2016,
Voprosy pitaniia,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
December 2019,
Molecular and cellular endocrinology,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
March 1990,
Biochimica et biophysica acta,
Q Dong, and
R M Lazarus, and
L S Wong, and
M Vellios, and
D J Handelsman
August 1995,
Archives of physiology and biochemistry,
