The Time Course of the Changes in Lactate Produced by Incisions in the Rat

Cha, Young Deog; Lee, Hong Sik; Han, Jeong Uk; Jung, Jong Kwon; Lee, Choon Soo; Shin, Sung Ho; Lim, Hyun Kyoung; Kim, Tae Jung

Abstract

BACKGROUND
It is well known that the level of lactate increases in wounds, which is not necessarily caused by a limitation of oxygen delivery, so may not primarily indicate ischemia. In this study, we measured the time course of the changes in the concentrations of lactate produced by incisions at 3 different sites (hind paw, gastrocnemius muscle and paraspinal area) in order to find factors that may activate and sensitize the nociceptors at the incision sites. METHODS: Incisions were made in either one side of plantar aspect of hind paw, paraspinal area or gastrocnemius muscle. The other side of each rat received a sham incision. Microdialysis fibers were inserted into the incisional area and sham incisional side of each rat on postoperative days 0, 1, 2, 4, 7 (8), 10 and 14. The concentrations of tissue lactates were then measured and compared. RESULTS: In the hind paw, the concentration of tissue lactate increased on the day of incision and on postoperative days 1 through 7, but was no different to that of the control paw on days 10 and 14. In the gastrocnemius muscle, the lactate concentration increased on postoperative days 1 through 4, and the paraspinal lactate also increased on the day of incision and on postoperative days 1 through 8, but had normalized by postoperative day 14. CONCLUSIONS: These data suggest that tissue lactate level increases after incisions, and is in part, parallel to the pH and pain behaviors caused by the incisions. Together, high lactate and low pH may contribute to incisional pain.