Journal of Applied Physiology, Vol 62, Issue 2 622-627, Copyright © 1987 by American Physiological Society
Exercise- and cold-induced changes in plasma beta-endorphin and beta-lipotropin in men and women
M. Viswanathan, J. P. Van Dijk, T. E. Graham, A. Bonen and J. C. George
The plasma beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) response
of men, eumenorrheic women, and amenorrheic women (n = 6) to 1 h of rest or
to a bicycle ergometer test [20 min at 30% maximum O2 uptake (VO2max), 20
min at 60% VO2max, and at 90% VO2max to exhaustion] was studied in both
normal (22 degrees C) and cold (5 degrees C) environments. beta-EP and
beta-LPH was measured by radioimmunoassay in venous samples collected every
20 min during rest or after each exercise bout. Exhaustive exercise at
ambient temperature (Ta) 22 degrees C induced significant increases in
plasma beta-EP and beta-LPH in all subjects as did work at 60% VO2max in
amenorrheic and eumenorrheic women. During work at Ta 5 degrees C, the
relative increase in beta-EP and beta-LPH was suppressed in eumenorrheic
women and completely prevented in amenorrheic women. Although significant
lowering of beta-EP and beta-LPH was observed in men and eumenorrheic women
during rest at 5 degrees C, amenorrheic women maintained precold exposure
levels. These findings suggest that plasma beta-EP and beta-LPH may reflect
a thermoregulatory response to heat load. There appears to be a sexual
dimorphism in exercise- and cold-induced release of beta-EP and beta-LPH
and amenorrhea may be accompanied by alterations in these responses.
