AJP - Gastrointestinal and Liver Physiology, Vol 251, Issue 6 859-G865, Copyright © 1986 by American Physiological Society
The relationship of ornithine decarboxylase and thymidine kinase to mirex-induced liver growth
J. D. Yarbrough, J. M. Grimley and P. I. Karl
To investigate the sequence of events that occur in the liver during
mirex-induced adaptive liver growth, [3H]thymidine incorporation into DNA,
thymidine kinase (TK), and ornithine decarboxylase (ODC) were studied in
intact and adrenalectomized (ADX) mirex-dosed rats, and the responses were
compared with experimental groups receiving corticosterone. In intact
mirex-dosed rats (a response that is both hyperplastic and hypertrophic)
there was a 36-h peak in ODC activity, and a 48-h peak in both
[3H]thymidine incorporation into DNA and TK activity. This was accompanied
by a 72% increase in relative liver weight (RLW). In contrast, in ADX
mirex-dosed rats (a predominately hyperplastic response), there was a
biphasic ODC response (18- and 36-h peaks), a 36-h TK peak, and a 48-h peak
in [3H]thymidine incorporation into DNA. Both TK activity and [3H]thymidine
incorporation into DNA were significantly elevated for the remainder of the
96-h study period. There was a 38% increase in RLW. Corticosterone
supplements to mirex-dosed intact rats resulted in a biphasic peak of TK
activity (30- and 48-h peaks), a reduced ODC peak at 36 h, and a 48-h peak
in [3H]thymidine incorporation into DNA. RLW response was similar to the
response in intact mirex-dosed rats. Corticosterone supplements to
mirex-dosed ADX rats eliminated the 48-h peak of [3H]thymidine
incorporation into DNA, reduced TK activity and shifted the peak to 30 h,
and eliminated the ODC biphasic response. The RLW increase was similar to
the response in intact mirex-dosed rats with a maximum 80% increase at 72 h
postmirex dose.
