AJP - Endocrinology and Metabolism, Vol 255, Issue 4 E482-E487, Copyright © 1988 by American Physiological Society
Gonadotropin-releasing hormone sensitivity in underfed prepubertal female rats
K. M. Lively and B. E. Piacsek
Department of Biology, Marquette University, Milwaukee, Wisconsin 53233.
Studies were conducted to investigate the effect of reduced food intake on
pituitary gonadotropin-releasing hormone (GnRH) sensitivity as a possible
link in the delay of puberty by underfeeding. Immature female rats (30-32
days old at the start of each experiment) were used throughout the study.
Rats on reduced food intake (R) received 60% of normal food intake
beginning at the age of 21 days, whereas control (C) animals were fed ad
libitum. In ovariectomized (OVX), estradiol benzoate-progesterone-treated R
rats, low doses (less than 5 ng/100 g body wt) of GnRH injected
intravenously produced higher serum luteinizing hormone (LH) concentration
than in comparable C rats. No difference was found at 5 ng GnRH but
response to high doses (15 and 45 ng/100 g body wt) was sharply reduced in
R rats. No difference in serum follicle-stimulating hormone concentrations
was found. In contrast to the OVX-steroid treated animals, in intact R
rats, GnRH evoked higher serum LH concentrations at both low and high
doses. These studies indicate that reduced caloric intake can affect
pituitary GnRH sensitivity and that the effect depends on both the dose of
GnRH and the internal, gonadal steroid hormone milieu.
