Androgen synthesis and aromatization by equine corpus luteum microsomes.

This research focuses on the process of androgen synthesis and aromatization within the corpus luteum in horses. The study found that under certain conditions, the corpus luteum can produce estrogens and androgens, and the enzymes responsible for these processes are closely related to those present in the equine testis.

Experimental Process

• The research began with a study on the mare corpus luteum – a temporary gland formed in the ovary of mammals after ovulation. Typically, this organ does not produce androgens (male sex hormones) or estrogens (female sex hormones) in vivo, meaning within the live horse.
• However, when the researchers incubated microsomes (small vesicles within the cell) from the mare corpus luteum with progesterone – a type of steroid hormone, and NADPH – a coenzyme used in anabolic reactions, the production of 17 alpha-hydroxyprogesterone and estrogen was observed.
• This mixture also yielded a small amount of androstenedione, another type of androgen which can be converted into testosterone or estrogen.

Impact of Aromatase Inhibitor

• When an aromatase inhibitor (4-hydroxyandrostenedione) was introduced in the experimental mixture, the accumulation of 17 alpha-hydroxyprogesterone and androstenedione was observed.
• This indicates that the aromatase inhibitor prevented the conversion of these androgens into estrogens, leading to their build-up.

Aromatization Process

• The study demonstrated a clear process of aromatization of testosterone and androstenedione, involving the stereospecific loss of 1 beta, 2 beta hydrogen atoms. This process was obstructed by MgCl2, KCl, and EDTA, which suggests their inhibiting role in the aromatization process.

The Role of Estrogen Synthetase and Aromatase

• The researchers went on to measure the Km value of estrogen synthetase – an enzyme involved in the synthesis of estrogens, from the equine corpus luteum for testosterone and androstenedione, which indicates the enzyme’s affinity for these substrates.
• 19-Norandrogens were found to be aromatized with slightly higher efficiency than regular androgens, despite the lower affinity of the aromatase enzyme for 19-norandrogens.
• The study concluded that aromatases – enzymes responsible for the conversion of androgens to estrogens, from the equine testis and corpus luteum are closely related.

Key Takeaways and Inquiries for Future Research

• This research brings attention to the possible coupling between the cell origin, synthesizing abilities, and in vivo production of the corpus luteum across different mammalian species.
• Further research must be conducted to explore the reasons for the varying hormone production capabilities of the corpus luteum in different species.