In utero and in vitro proteinase activity during the Mesocricetus auratus embryo zona escape time window

Abstract

The goal of the present study was to investigate proteinase activity in uterine flushates collected during the zona loss time window (68-80 h post-egg activation) in both pregnant and pseudopregnant hamsters and in culture medium conditioned by hatching blastocysts. Several prominent enzyme activities appeared in all pregnant and pseudopregnant uterine flushates. However, only a 45, 43 × 10-3 Mr doublet coincided with the zona loss time window; these bands were absent outside of this time window and were not found in conditioned medium. In medium conditioned by hatching blastocysts, enzyme activity was represented by a 70, 65 × 10-3 Mr doublet identical to a doublet seen in all uterine flushates collected and in serum. There were 12 pregnant and 8 pseudopregnant uterine flushates that were capable of zona lyric activity in vitro (positive bioassays). Of these positive bioassays, five pregnant and four pseudopregnant uterine flushates exhibited the 45, 43 × 10-3 Mr doublet (correlative positive bioassays). These data suggest that there is an important uterine contribution to blastocyst escape from the zona pellucida, consisting of proteinases secreted during a finite time window prior to blastocyst attachment that are different from the proteinases responsible for the zona lyric activity in vitro.