DEMONSTRATION OF THE INTRALOBULAR LYMPHATICS IN THE GUINEA GIG PANCREAS BY AN ENZYME-HISTOCHEMICAL METHOD

Intralobular lymphatics in the guinea pig pancreas were demonstrated e nzyme-histochemically showing the extent, distribution and line struct ure by combined light and transmission electron microscopy. 5'-nucleot idase(5'-Nase)-positive lymphatic vessels were present throughout the pancreas. Intralobular lymphatics among the acini were comparatively r are and generally independent of the blood capillaries, pancreatic duc ts and acini. These lymphatics revealed the usual structural features, such as typical intercellular junctions and very tenuous vascular wal ls without continuous basal laminae. Fine precipitates of the cerium-b ased reaction product for 5'-Nase activity were found to be associated with cell membranes of the lymphatic endothelium and pinocytotic vesi cles. Lymphatics were not closely related to the endocrine islets, alt hough alkaline phosphatase(ALPase)-positive blood capillaries were wel l developed. Collecting lymphatic vessels with valves with weaker 5'-N ase activity were also detected in the interlobular connective tissue. ALPase activity, absent in the lymphatics, was positive in the blood capillaries, suggesting that it is also a useful way demonstrating, hi stochemically, the blood capillaries in the guinea pig pancreas.