Sequential changes in plasma luteinizing hormone and plasma prorenin during the menstrual cycle

Area of Science:

• Reproductive Endocrinology
• Hormonal Regulation
• Biochemistry

Background:

• Prorenin, the inactive precursor to renin, is primarily secreted by the kidneys.
• Cyclical increases in plasma prorenin during the menstrual cycle suggest ovarian involvement.
• The role of ovarian prorenin and its regulation by pituitary hormones remains unclear.

Purpose of the Study:

• To investigate the temporal relationship between plasma prorenin and luteinizing hormone (LH) during the midcycle period.
• To determine if LH stimulates ovarian prorenin secretion in normal women.
• To explore the potential role of prorenin in ovulation and ovarian renin system activity.

Main Methods:

• Blood samples collected daily for 7 days from nine women during the midcycle.
• Intensive blood sampling every 8 hours for 6 days from six women.
• Plasma prorenin, LH, and estradiol levels were measured, with LH peak as time zero.

Main Results:

• The initial rise in LH preceded the rise in prorenin by approximately 16 hours.
• The LH peak occurred 8-16 hours before the prorenin peak, despite high estradiol levels.
• Plasma prorenin remained elevated longer than LH and estradiol after their decline.

Conclusions:

• Gonadotropins, specifically LH, appear to stimulate ovarian prorenin release.
• The timing and concentration of prorenin suggest a role in ovulation and ovarian renin system function.
• Ovarian prorenin may regulate an independent ovarian renin system distinct from circulating active renin.