OBJECTIVETo observe the expression of beta-endorphin and micro-opioid receptor (MOR) during wound healing process in rat with deep partial-thickness scald.

METHODSThirty-six Wistar rats were randomly divided into control( n = 6, without treatment) , and scald ( n = 30, with 5% TBSA deep-partial thickness scald) groups. Skin specimens from wound were harvested immediately after scald and on 3, 7, 14, 21 post-scald days( PSD) for the determination of 1-endorphin and MOR expression with immunofluorescent staining.

RESULTSbeta-endorphin and MOR were mainly distributed in nerve terminal at the border of dermis and epidermis , keratinocyte in some epidermis , in the fibroblast in dermis , with a weak expression The expression of beta-endorphin peaked in whole layer of skin on 3 PSD( 196 +/-16, P <0. 01) ,while that of MOR was concentrated in keratinocytes in the basal layer and the basement membrane. The expression of MOR was strengthened on 7 PSD with disarrangement of collagen , and it peaked on 14 PSD (306 +/- 23, P < 0.01) with epithelization in some wounds. There was still strong expression of beta-endorphin on 7 and 14 PSD. Complete epithelization was observed in scald group on 21 PSD, with nerve terminal approaching the boundary between the dermis and epidermis, and collagen began to arrange in good order. The expression of P-endorphin in scald group (31 +/-24)was similar to that in control group(30 +/- 18) on 21 PSD, but the expression of MOR (56 +/- 16) was still higher than that in control group (28 +/- 15 ).

CONCLUSIONThe expression of MOR and P-endorphin exhibits chronobiological nature during the process of wound healing,