Journal of Applied Physiology, Vol 38, Issue 2 245-249, Copyright © 1975 by American Physiological Society
Nature of induction of tryptophan pyrrolase in cold exposure
V. Sitaramam and T. Ramasarma
The activity of hepatic tryptophan pyrrolase in rats exposed to cold
increased rapidly and reached a maximum of three-fold at 8 h. On continued
exposure up to 48 h stress, the activity partly decreased but remained at a
level higher than the initial. Withdrawal from the cold stress reversed the
change. Adrenalectomy or treatment with inhibitors of protein synthesis
abolished the increase in the enzyme activity during cold stress indicating
a possible involvement of corticosteroids and de novo protein synthesis.
Treatment with drugs known to block autonomic nervous system failed to
inhibit the cold-mediated increase in enzyme activity. The results suggest
that the increase in enzyme activity obtained on cold exposure is mediated
by corticosteroids and not by either indoleaklylamines or autonomic nervous
system. The changes in the enzyme obtained under cold stress with respect
to the overshoot phenomenon, relationship to the degree of stress and
reversibility on withdrawal from the stress indicate the "adaptate" nature
of the response.
