Mitochondrial cholesterol availability during gonadotropin-induced Leydig cell desensitization

Area of Science:

• Endocrinology
• Biochemistry
• Reproductive Biology

Background:

• The androgen biosynthetic pathway in Leydig cells is crucial for male reproductive function.
• Human chorionic gonadotropin (hCG) and luteinizing hormone (LH) regulate Leydig cell steroidogenesis.
• Understanding early lesions in this pathway is key to identifying regulatory mechanisms.

Purpose of the Study:

• To define the early lesion (before pregnenolone formation) in androgen biosynthesis induced by hCG or LH.
• To optimize aminoglutethimide dosing for sustained steroidogenesis inhibition in vivo and in vitro.
• To investigate the role of cholesterol metabolism and side-chain cleavage activity.

Main Methods:

• Optimized aminoglutethimide dosing for maximal and sustained inhibition of steroidogenesis.
• Administered aminoglutethimide in vivo and in vitro to Leydig cells.
• Measured testosterone, pregnenolone, and cholesterol levels.
• Assessed Leydig cell steroidogenic capacity and cholesterol conversion.

Main Results:

• Aminoglutethimide inhibited Leydig cell steroidogenesis dose-dependently.
• Optimal serum concentration for maximal inhibition was 100 micrograms/ml.
• Circulating aminoglutethimide half-life decreased with prolonged treatment.
• High-dose aminoglutethimide prevented the late lesion but not the early lesion induced by hCG.
• Aminoglutethimide increased cholesterol accumulation and pregnenolone production in vitro, but conversion was blocked in the early lesion.

Conclusions:

• The early lesion in desensitized Leydig cells is due to inhibition of side-chain cleavage activity, not reduced cholesterol availability.
• Sustained high levels of aminoglutethimide are required to inhibit cholesterol metabolism.
• A specific dosing schedule for aminoglutethimide was established for studying steroidogenesis.
• Findings support a model where early hCG/LH-induced lesions impair cholesterol conversion to pregnenolone.