Signal transduction, second messenger, and protein kinase responses
during freezing exposures in the wood frog.
Holden, Clark P., and Kenneth B. Storey.
Institute of Biochemistry and Department of Biology, Carleton
University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S
5B6
APStracts 3:0155R, 1996.
Changes in the percentage of cyclic AMP-dependent protein kinase
present as the active catalytic subunit (PKAc) and in the levels of
the second messengers adenosine 3':5'-cyclic monophosphate (cAMP),
guanosine 3':5'-cyclic monophosphate (cGMP), and D-myo-inositol
1,4,5-trisphosphate (IP3) were quantified in tissues of the freeze
tolerant wood frog Rana sylvatica over the course of freezing at -2.5
degrees C and thawing at 5 degrees C. Freezing exposure rapidly
raised liver [cAMP] and % PKAc (by 2- and 6-fold, respectively)
within 2 min post-nucleation; both peaked and stabilized between 5
and 60 min post-nucleation but declined with longer freezing. Other
organs also showed elevated PKAc during freezing, particularly
skeletal muscle. By contrast, [cGMP] was reduced in muscle and kidney
after 24 h freezing but rose after thawing in muscle. Liver also
showed a 2-fold elevation of cGMP during thawing. The protein kinase
C (PKC) second messenger, IP3, rose throughout freezing in liver
reaching 11-fold higher than control values after 24 h freezing. IP3
was also elevated in brain after 4 and 8 h freezing. The different
patterns of cAMP, PKA and IP3 changes in liver suggest that whereas
cAMP and PKA clearly mediate the rapid activation of glucose output
as a cryoprotectant, IP3 and PKC may be involved instead with
metabolic responses that deal with the consequences of long term
freezing such as ischemia resistance or cell volume control.
Received 18 January 1996; accepted in final form 12 April 1996.
APS Manuscript Number R28-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96