Lead citrate

The ileum sections of rats were dissected and cut into ultrathin (70–90 nm) sections. After dehydration, ultrathin sections were stained with uranyl acetate (SPI-CHEM, West Chester, USA) and lead citrate (Sinopharm Chemical Reagent, Shanghai, China), and then examined by transmission electron microscopy. Images were taken using an H‐7650 electron microscope (Hitachi, Tokyo, Japan) in a blinded manner.

HE staining was performed on the portal vein, central hepatic vein and vasa intestinae tenuis of rats in different groups 24 h following surgery. Tissue samples were fixed in 2% paraformaldehyde overnight at 4°C. Tissue samples were dehydrated by ascending ethanol series (50, 70, 80 and 90% ethanol each for 15 min, 70% ethanol overnight, and 100% ethanol for 20 min), soaked in acetone twice for 15 min and embedded in Araldite. Following 48-h polymerization at 65°C, the embedded tissue samples were cut into ultrathin slices (70 nm) using an ultramicrotome (EM UC7; Leica Microsystems GmbH, Wetzlar, Germany). Tissue sections were stained with hematoxylene for 4 min at room temperature and couter stained with eosin for 90 sec at room temperature, and observed under a light microscope (YYS-190E; Shanghai Optical Instrument, Shanghai, China) at a magnification ×100 and ×400.
TEM were performed on the portal vein of rats in different groups. Tissue slices were prepared as described above. Following staining with uranyl acetate and lead citrate (both Sinopharm Chemical Reagent Co., Ltd., Beijing, China) each for 10 min at room temperature, the samples were observed by TEM (JEM-1230; JEOL, Ltd., Tokyo, Japan) 6, 12 and 24 h after the surgeries.