The source of progesterone in rabbit blastocysts

Area of Science:

• Reproductive Biology
• Endocrinology
• Developmental Biology

Background:

• Progesterone is vital for maintaining pregnancy.
• The source of progesterone during early pregnancy in rabbits is not fully elucidated.

Purpose of the Study:

• To investigate the source and levels of progesterone during early pregnancy in rabbits.
• To determine the role of maternal ovaries in supporting rabbit blastocyst development.

Main Methods:

• Measurement of progesterone levels in blastocysts, uterine fluid, and sera of pregnant rabbits.
• Comparison of progesterone levels in intact pregnant rabbits versus bilaterally ovariectomized rabbits treated with medroxyprogesterone acetate.

Main Results:

• High progesterone concentrations were detected in blastocysts, uterine fluid, and sera of normally pregnant rabbits on Days 6-7.
• Bilaterally ovariectomized rabbits showed significantly reduced progesterone levels (<2% of control) even with exogenous hormone administration.

Conclusions:

• Maternal ovaries are the primary source of high progesterone levels supporting the rabbit blastocyst during early pregnancy.
• The rabbit blastocyst relies heavily on ovarian-derived progesterone for successful implantation and early development.