Loss of Absorbed Lipid during Fixation and Dehydration of Jejunal Mucosa

No neutral lipid, but nearly all the phospholipid, was retained in Acanthamoebae when this organism was fixed in osmium tetroxide and dehydrated with ethanol. If applicable to intestinal mucosa, this observation of Korn and Weisman's (I) might disturb electron microscopists striving to interpret morphological events during fat absorption. Three other groups of investigators have commented on the preservation of tissue lipid after it had been processed for electron microscopy. Morgan and Huber (2) recovered less than 40% of lung lecithin-3H after this tissue had been fixed with osmium tetroxide and dehydrated with ethanol. On the other hand, Stein and Stein (3) reported that 70-78% of liver lipid-3H was preserved. When hamster small intestine was incubated with linolenic acid-'C, about 90% of the mucosal 14C was found in the fixed and dehydrated tissue.' These varying results suggest that the chemical structure of intracellular lipids and the type of tissue determine what lipids are removed during processing for electron microscopy. Furthermore, losses of indigenous tissue lipid and of newly absorbed lipid may not be similar. The present study was designed to quantify the loss of absorbed lipid from intestinal mucosa which had been exposed in vivo to saturated or unsaturated lipid, fixed in buffered osmium tetroxide, and dehydrated in graded ethanols as for electron microscopy.