AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 6 1359-R1364, Copyright © 1989 by American Physiological Society
Effects of prolonged exercise on puberty and luteinizing hormone secretion in female rats
J. M. Manning and F. H. Bronson
Department of Zoology, University of Texas, Austin 78712.
Immature female rats were required to run for prolonged periods of time to
obtain food. The amount of food they earned was adequate for full pubertal
development and moderate growth under nonworking conditions, but both
processes were blocked by the exercise requirement. Prolonged exercise also
blocked the pulsatile release of luteinizing hormone (LH); only two LH
pulses were seen in seven exercising females during a total of 24 h of
monitoring at 8 wk of age. By comparison, almost 1 pulse/h was seen in
postpubertal, normally growing females of this same age during metestrus.
When the exercising females' running requirement was relaxed at 8 wk of age
they experienced rapid catch-up growth and reproductive development. Both
basal secretion and LH pulse frequency increased markedly within 48 h, and
most of these females ovulated during the third dark period after
relaxation. Altogether, the experimental paradigm and techniques employed
here yield highly predictable results, and they should prove useful for
exploring other neuroendocrine pathways through which excessive exercise
antagonizes reproduction.
