Immunoreactive endothelin-1, endothelin-2 and big endothelin-1 in follicular fluids of women undergoing ovulation induction for in-vitro fertilization

Endothelin-like immunoreactivity specific for endothelin-1 (ET-1),endothelin-2 (ET-2) or big endothelin-1 (big ET-1) was measured,using commercially available radioimmuno-assay kits, in follicularfluid collected at the time of oocyte aspiration from 36 womenundergoing ovulation induction by human menopausal gonadotrophin(HMG). The relation-ship of ET concentrations to HMG dose, peakserum oestra—-diol concentration, the number and sizeof follicles (by ultrasound), the number of retrieved oocytesand the fertilization rate per retrieved oocyte were studied.Overall, 94% of follicular fluid samples were positive for ET-1,92% were positive for ET-2, and 100% were positive for big ET-1.Mean ET-1, ET-2 and big ET-1 concentrations were 17.23±12.20,32.42± 14.32 and 34.55± 16.34 pg/ml respectively.Endo-thelin-like immunoreactivity in follicular fluid sampleswas found in an order of ET-1<ET-2< big ET-1. There wasa highly significant positive correlation (r=0.8711, P=0.0001,n=32) between follicular ET-1 and ET-2 concentrations. No significantcorrelation of follicular big ET-1 was established either withET-1 or ET-2. However, big ET-1 was found to be negatively correlatedwith number of oocytes (P=0.03) and number of follicles (P=0.04).Control plasma ET-1 and follicular ET-1 were not significantlydifferent. There was no significant correlation between ET concentrationsand any of the other studied parameters. The results demonstratedthat immunoreactive ET-1, ET-2 and big ET-1 exist in human follicularfluid collected at the time of oocytes retrieval for in-vitrofertilization and may be involved in the regulation of reproductivefunction. The clinical significance and physiological role offollicular fluid ET deserve further studies.