POST-MORTEM CHANGES IN SUBCELLULAR FRACTIONS FROM NORMAL AND PALE SOFT EXUDATIVE PORCINE MUSCLE .2. ELECTRON MICROSCOPY

SUMMARY— Myofibrillar, mitochondrial, heavy sarcoplasmic reticulum, and light sarcoplasmic reticulum fractions were isolated from homogenates of normal and pale, soft, exudative (PSE) porcine muscle at 0 and 24 hr post‐mortem and examined by electron microscopy. No differences were observed between normal and PSE myofibrils obtained at death. PSE myofibrils prepared at 24 hr post‐mortem had more granular appearing filaments and wider Z lines than normal myofibrils at 24 hr. The PSE heavy sarcoplasmic reticulum fraction obtained at death had a higher proportion of granular material than the same fraction from normal muscle. Several structural differences between the other PSE and normal fractions were also observed, especially at 24 hr postmortem. This study indicated that the composition of the subcellular fractions changed with time post‐mortem and that this change should be considered when analyzing biochemical data from these fractions. However, the differences observed could not explain the large changes in calcium accumulating ability that have been shown to occur post‐mortem. Copyright © 1969, Wiley Blackwell. All rights reserved