Luteotrophic effect of the rabbit blastocyst

Area of Science:

• Reproductive biology
• Endocrinology
• Mammalian reproduction

Background:

• Progesterone is crucial for establishing and maintaining pregnancy in mammals.
• Understanding early hormonal changes is key to reproductive success.

Purpose of the Study:

• To investigate progesterone profiles during early pregnancy and pseudopregnancy in rabbits.
• To determine the impact of blastocyst transfer on progesterone levels.

Main Methods:

• Radioimmunoassay was used to measure daily peripheral plasma progesterone concentrations in 27 rabbits from Day 1 to 7.
• Comparison of progesterone levels between pregnant, pseudopregnant, and sham-operated rabbits.
• Assessment of progesterone changes following blastocyst transfer.

Main Results:

• Progesterone levels showed a significantly higher rate of increase in pregnant rabbits compared to pseudopregnant rabbits from Day 5 to 7.
• Progesterone levels did not differ significantly between groups before Day 5.
• Transfer of Day-4 or -5 blastocysts led to a significant increase in progesterone compared to controls and pseudopregnant does.

Conclusions:

• Progesterone elevation by Day 5 is a key indicator of successful pregnancy establishment in rabbits.
• Blastocyst viability and uterine environment significantly influence progesterone production, crucial for pregnancy maintenance.