Objective: To determine the concentrations of tumor necrosis factor (TNF)alpha, interleukin (IL)beta, IL-6 and IL-8 and the expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in the lower uterine segment during parturition at term and to investigate correlations with the stage of cervical dilatation and with the duration of labor.
Patients and methods: Biopsy specimens were taken from the lower uterine segment of 59 women undergoing non-elective cesarean sectin at term at different stages of cervical dilatation (< 2 cm, n = 17; 2-3 cm, n = 12; 4-6 cm, n = 13; > 6 cm, n = 17) after varying length of the time in labor (1-6 h, n = 18; > 6-12 h, n = 16; > 12-24 h, n = 15; > 24 h, n = 10). The concentrations of TNF alpha, IL-1 beta, IL-6 and IL-8 in protein extracts of these specimens were determined by enzyme linked immunosorbent assays and the expression of ELAM-1 and VCAM-1 was studied by immunohistochemistry. Staining was considered negative if < 5% of the endothelial cells were stained and positive if > or = 5% were stained.
Results: At < 2 cm dilated cervix the median concentrations of TNF alpha, IL-1 beta, IL-6 and IL-8 were 8.0 pg/mg total protein (TP), 1.3 pg/mg TP, 12.6 pg/mg TP and 17.2 pg/mg TP, respectively. At 4-6 cm dilatation the median concentrations were increased (TNF alpha: 22.2 pg/mg TP [P = 0.05], IL-1 beta: 22.2 pg/mg TP [P < 0.05], IL-6: 1226 pg/mg TP [P < 0.05], IL-8: 2081 mg/mg TP [P < 0.05]). At > 6 cm dilatation no further increase was observed. The expression of ELAM-1 and VCAM-1 was significantly greater at > 6 cm dilatation than < 2 cm dilatation (P < 0.001 and 0.05, respectively). With increasing duration of labor, the concentrations of IL-1 beta, IL-6 and IL-8 (but not of TNF alpha) increased and were significantly higher at > 6 cm dilatation than at < 2 cm (P < 0.05). Expression of ELAM-1 and VCAM-1 did not vary with duration of labor.
Conclusions: These first investigations of cytokines and cell adhesion molecules in the lower uterine segment at both different stages of cervical dilatation and different duration of labor support the decisive role of cytokines for normal cervical dilatation. Local changes in the lower uterine segment independent from the effects of labor (e.g. increase of endothelial adhesivity) seem to be of special importance in this process.