Fine structure observations on rat jejunal epithelial cells during fat processing and resorption following L-81 exposure and reversal.

In order to more easily follow membrane interaction following L-81 administration and subsequent lipid processing tannic acid was used to highlight cell membrane contrast in intestinal epithelial cells of Sprague-Dawley male rats. Jejunal epithelial cells were examined with the electron microscope following 4 h of L-81 administration and 45 min, 1, 1.5 and 2 h after the cessation of L-81 administration. After 4 h of L-81 administration the apical cytoplasm was seen to be filled with large, lipid droplets limited by a single, 4-5 nm thick, electron-dense rim. During the reversal process changes noted in the cytoplasm included the following. As early as 45 min clear and electron-dense-filled vesicles appeared scattered in the apical cytoplasm and juxtaposed to the lipid droplets. The large, non-membrane bound lipid droplets decreased in size and number over the two hour period while the number and size of electron-dense containing vesicles increased. The vesicles were subsequently found concentrated in the Golgi region where assimilation and production of chylomicron and VLDL size particles occurred. Eventually multiple groups of such particles were found intercellularly and basally. Thus the re-cycling of lipid and chylomicron production and secretion following L-81 reversal is similar to that following experimental studies on normal fat over-loading and following recovery after puromycin treatment. This data is discussed in light of previous data on fat processing and secretion in rat intestinal epithelial cells with particular reference to membrane events visible following tannic acid membrane highlighting.