Progesterone induces Ca++-dependent 3',5'-cyclic adenosine monophosphate increase in human sperm

Area of Science:

• Reproductive Biology
• Sperm Physiology
• Molecular Endocrinology

Background:

• Progesterone (P) modulates sperm function via plasma membrane binding.
• Sperm hyperactivation is a crucial process for fertilization and is cAMP-dependent.

Purpose of the Study:

• To investigate the effect of progesterone on cyclic adenosine monophosphate (cAMP) levels in human spermatozoa.
• To elucidate the calcium (Ca++) and receptor mechanisms underlying progesterone-induced cAMP changes and sperm hyperactivation.

Main Methods:

• Human spermatozoa were incubated with varying progesterone concentrations and time points.
• Cyclic adenosine monophosphate (cAMP) levels and sperm hyperactivation percentages were measured.
• Experiments were conducted with and without extracellular Ca++, and with calcium ionophore A23187, GABA, picrotoxin, genistein, and RU486.

Main Results:

• Progesterone dose-dependently increased cAMP levels, with significant peaks at 30 and 120 minutes.
• These cAMP increases correlated with enhanced sperm hyperactivation.
• Progesterone's effects on cAMP were abolished in the absence of Ca++ and mimicked by calcium ionophore A23187.
• The effects were partially reproduced by GABA and inhibited by picrotoxin and genistein, but not RU486.

Conclusions:

• Progesterone induces a Ca++-dependent increase in cAMP in human sperm.
• This effect is likely mediated by Ca++ influx and involves GABA(A)-like receptors.
• The findings provide insights into the molecular mechanisms regulating sperm function and hyperactivation.