A cryoclamp for the rapid cryofixation of the isolated blood-perfused rabbit cardiac papillary muscle preparation at predefined times during the contraction cycle

There is increasing evidence that the distribution of monovalent cations in cardiac cells may be non-uniform, particularly in the region immediately b eneath the sarcolemma, and we have proposed that a build-up of sodium in th is region could be an important factor in the development of ischaemia-repe rfusion injury. Electron probe X-ray microanalysis is ideal for the study o f such changes in distribution but the application of the technique to this problem imposes severe requirements on the specimen and on the method for cryofixation. The specimen must be perfused through its vasculature so that it can be made truly ischaemic and be successfully reperfused. It is neces sary to be able to cryofix the specimen without disturbance of its blood su pply, electrical stimulation or temperature. Tt is also important to know t he time in the contraction cycle when cryafixation occurs. Here we describe the design of an automated cryofixation device which can be used to cryofi x a blood perfused papillary muscle preparation at predetermined time point s in the contraction cycle. Preliminary data obtained from the analysis of rabbit papillary muscles subjected to varying periods of ischaemia are incl uded as an example of the use of the cryoclamp.