Signal transduction and the function of second messengers and protein kinases in the control of glycogenolysis and cryoprotectant production in freeze tolerant vertebrates

A unique group of lower vertebrates, termed freeze tolerant, have developed complex biochemical mechanisms that allow them to survive whole body freezing. Perhaps the most important of these mechanisms is the production of cryoprotectant, usually in the form of glucose, via an activation of glycogenolysis as a response to freezing. This thesis investigates: (1) whether protein kinase enzymes are responsible for the early activation of glycolysis that stimulates cryoprotectant production in freeze tolerant vertebrates and/or the subsequent inhibition of the pathway in the later stages of a freezing episode, (2) the comparative aspects of the responses of protein kinases elicited by the environmental stresses of dehydration and anoxia, to those of freezing, and (3) the role of the free catalytic subunit of cyclic AMP-dependent protein kinase (PKAc) and protein kinase C (PKC) in cryoprotectant production in Rana sylvatica liver.;Short freezing episodes caused a dramatic increase in the percentage of free catalytic PKA (PKAc). This response diminished with increased time frozen in tissues of freeze tolerant vertebrates. The measurement of second messengers over a freezing time course revealed significant increases in adenosine 3...