Abstract: Objective Through comparing the slides qualities and periodic acid Schiff (PAS) staining effects with three different fixatives and fixed time on the normal liver, kidney, small intestine from mice, so as to select the optimum fixed methods. Methods The liver, kidney and small intestine tissue from adult male C57BL/6 mice were harvested, then fixed in three fixatives with different times respectively, the 4% paraformaldehyde fluid with 24 h, 48 h, 72 h, the Carnoy’s fluid with 4 h, 8 h, 12 h, and the Bouin’s fluid with 12 h, 24 h, 48 h. After fixed sufficiently, produced paraffin section and then stained routinely with PAS, to observe the staining effect under microscope. Result Different PAS staining results existed among three fixatives with different fixed time on three kind of tissues. The best staining result was observed in Carnoy’s fluid fixed for 12 h, the 4% paraformaldehyde fixed 48 h can basically met the criteria for observation. the staining result was relatively poor fixed in Bouin’s fluid. Conclusion PAS reaction was selective for fixative and fixed time. Carnoy’s fluid is an ideal fixative, but based on the fixed effect, repeatability, safety, and cost, 4% paraformaldehyde fluid can replace Carnoy’s liquid and widely used in PAS reaction.

Key words: Carnoy fluid, Bouin's fluid, Paraformaldehyde fluid, Periodic acid Schiff (PAS) staining