Abstract:
Expanded blastocysts collected from superovulated Sarda ewes were divided atrandom into four groups for culture in a simple medium that does not supportblastocyst hatching (CZB) or a complex medium that is permissive to hatching(TCM 199), with or without vasoactive intestinal peptide (VIP), a known embryomitogenic peptide. Plasminogen activator (PA) secretion after 24 h of culture,and the number of cells, diameter of blastocysts and hatching rate after 48 hof culture were compared. The results showed an increase in hatching rate(78.6 v. 6.7%; P<0.01),diameter and number of cells (220.89 v. 210.44 m,P<0.01 and 246 v. 232,P<0.01 respectively) and caseinolytic areas (1.33v. 0.92 cm, P<0.01) ofblastocysts cultured in TCM 199 compared with those cultured in CZB.Supplementation of the culture media with VIP increased these parameters inCZB (P<0.01) and partially in TCM 199. In particular,cell number, diameter and PA activity were significantly higher(P<0.01) after culture with VIP in both media.Immunoneutralization of exogenous VIP in culture with anti-VIP antibody causeda decrease in the hatching rate (P<0.01) of embryoscultured in medium with VIP, similar to the rate in unsupplemented CZB(P<0.01). These results suggest a receptor-mediatedresponse. In immunohistochemical studies, VIP was shown to bind receptors inhatched blastocysts demonstrating the VIP-receptor interaction, and VIPreceptors of approximately 150 kDa were revealed by electrophoretic studies.In conclusion, ovine preimplantation embryos exhibit VIP receptors, providinga basis for a receptor-mediated influence of VIP in the hatching of ovineblastocysts.