Post-mortem storage of tissue for X-ray microanalysis in pathology.

Possible alternatives to rapid freezing in liquid nitrogen of tissue for X-ray microanalysis of electrolytes at the cellular level were investigated. These alternatives might be used in cases where tissue becomes available for examination, e.g., at autopsy, but liquid nitrogen is not immediately available. Rat submandibular gland was used as a test tissue. Freezing of pieces of tissue in a conventional freezer at -80 degrees C or even at -20 degrees C retained the elemental distribution at the cellular level, and also retained the difference between a 'normal' and a 'pathological' (mimicked by an injection of a high dose of isoproterenol) situation. Storage of tissue in a refrigerator, or delaying the autopsy in anticipation of the arrival of liquid nitrogen is not recommended. Significant changes in the cellular ion content occurred if the tissue was left in the animal for 24h post-mortem.