[Phase transition in lipids and the problem of homoiothermia].

Why such a high stability of temperature is necessary for warm-blooded animals? Why the range of body temperatures of various warm-blooded species is several-fold narrower than the range of environmental temperatures? What were the physicochemical factors that determined such results of the biological evolution? A hypothesis presented in this short communication provides answers to these basic questions of the problem of homoiothermia. The hypothesis implies that the Ca(2+)-induced chain-ordering phase transition in the lipid component of synaptic membranes plays a key role at the last step of the mechanism of synaptic transmission, namely, the step of neurotransmitter release. The physicochemical substantiation of a possible molecular mechanism of the release involving the phase transition is presented, and the main kinetic and evolutionary issues of the mechanism are considered in brief.