Post-Mortem Physiological and Morphological Changes of Rumen Mucosal Tissue

Rumen mucosa from the cranial sac was incubated in a volatile fatty acid medium, either immediately or after immersion in Krebs-Ringer (K-R) for 20 to 40 rain, to study methods of maintaining viability. The metabolic activity of mucosa immersed in 39 C K-R for 40 rain before incubation was not significantly different from that of mucosa incubated immediately; however, mucosa immersed in ice-cold K-R at 0 C for the same period was significantly less active. Immersion of mueosa in K-R at 39 C for 20 rain and then in K-R at 0 C for 20 rain did not reduce metabolic activity; whereas, reversing the treatments caused a marked reduction. In an attempt to explain the loss of metabolic activity after immersion at 0 C, rumen mucosa immersed in 39 C or 0 C K-R was compared with nonimmersed tissue from the gross to the ultrastructural level. The site of fl-hydroxybutyrate dchydrogenase action (involved in the metabolism of butyrate) was localized in the mitochondria of the epithelial layer of the mucosa with a standard histochemical technique. Electron microscopic studies indicated that immersion at 39 C caused an apparent coagulation of intracellular material and distortion of mitochondria, although cristae often are identifiable. Immersion in 0 C K-R resulted in a generally washed-out appearance, with distorted and exploded mitochondria, usually with an apparent lack of cristae.