Morphological and morphometric studies in pancreatic acinar cells of the rat at successive post-mortem intervals. The early appearance of a previously undescribed Golgi complex associated tubular vesicular structure.

Structural alterations in rat pancreatic acinar cells were studied in thin section at 0.5, 1, 4, 8, 12, 24 and 48 h post-mortem (PM). Morphometric analyses were performed both by light and electron microscopy, at 0.5 and 1 h PM. The parameters evaluated were: a) nuclear, cytoplasmic and cellular volumes; b) volume density and absolute volume of the rough endoplasmic reticulum (RER), mitochondria, zymogen granules (ZG), Golgi complex and its subcompartments [cisternae, condensing vacuole (CV) and 56-nm diameter vesicles], dense bodies (lysosome-like structures, electron-dense vacuoles and unidentifiable granules) and cytoplasmic matrix; c) surface density, surface/volume ratio and total surface area of the RER, mitochondria, ZG, Golgi cisternae, 56-nm diameter vesicles lying at the rough ER-Golgi interface, CV, and apical and basolateral membranes. Between 0.5 and 48 h, the mitochondria were dilated, junctional complexes were preserved and autophagic vacuoles were rare or absent. Flocculent densities were present in the mitochondria and chromatin condensation was observed at 4 h PM. In thin sections from samples obtained between 0.5 and 12 h, we consistently observed a membrane bounded structure formed by tubules and vesicles, designated as a tubular vesicular structure (TVS). These TVS's were observed at positions corresponding to the 4th Golgi cisterna. Fibrillar aggregates and a reduction in the number of 56-nm vesicles on the cis side of the Golgi were seen. Morphometry revealed a 60-70% reduction in the numerical density of the 56-nm vesicles between zero (control) and 0.5 h PM. These analyses also showed a 70% increase in the total volume and 57% increase in the total membrane surface of the Golgi cisternae in the PM period. The current results suggest that during the early PM (0.5 h) there is transport between Golgi compartments, and the 56-nm diameter vesicles fuse with the cisternae.