Objective    To better understand the regulation of the soluble receptor of vascular endothelial growth factor (VEGF)

s-VEGFR-1 (or soluble fms-like tyrosine kinase

SFlt-1)

in angiogenetic process in endometriosis.     Methods    Levels of free VEGF and s-VEGFR-1 were measured by enzyme-linked immunosorbent assay (ELISA) in peritoneal fluid from 28 subjects with surgically confirmed endometriosis

and 10 controls with no clinical evidence of the disease and other diseases. Meanwhile

we calculated a VEGF activity index by means of the ratio VEGF/s-VEGFR-1.     Results    We found higher VEGF concentration in endometriotic lesions than controls (P0.01) and VEGF concentration in stage Ⅲ-Ⅳ was higher than in stage Ⅰ-Ⅱ (P0.05). S-VEGFR-1 concentration followed a similar pattern with VEGF (P0.01)

but no statistically significant difference was found between stage Ⅲ-Ⅳ and stage Ⅰ-Ⅱ (P0.05). VEGF activity index in controls

stage Ⅰ-Ⅱ and stages Ⅲ-Ⅳ of endometriosis was 0.310

0.276 and 0.273

respectively. VEGF and s-VEGFR-1 concentration were also higher in proliferative phase than in secretory phase in endometriotic lesions (P0.01). VEGF activity index in proliferative phase was lower than in secretory phase of endometriosis.     Conclusion    VEGF certainly plays an important role in endometriosis and its progression. However

the activity index may be better to investigate the real role of VEGF in the pathology. s-VEGFR-1 can down-regulate VEGF activity.