# REGULATION OF STEROIDOGENIC ENZYMES IN LEYDIG CELLS

> **NIH NIH R01** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 1993 · $212,632

## Abstract

The long term objective of this project is to characterize the mechanisms
that determine the capcity of Leydig cells to produce testosterone.  We
have approached this problem by studying the relationship of activities of
steroid biosynthetic enzymes to maximal testosterone production in two
functionally distinct populations of Leydig cells from normal and
gonadotropin-treated rats.  The specific aims of the present study are
designed to evaluate additional sites in the steroidogenic pathway that may
be decisive in determining Leydig cell capacity for testosterone production
as well as to elucidate the mechanisms by which luteinizing hormone (LH)
and cAMP either increase or decrease maximal testosterone production
depending on the mode of their administration.  Specifically we will
determine:  1) whether the activity of the cholesterol side chain cleavage
enzyme (P-450scc) differs in the two populations of Leydig cells and
whether chronic in vivo treatment with LH increases the activity of
P-450scc' using homogenates or enriched mitochondrial fractions of Leydig
cells separated into two populations by Metrizamide gradient
centrifugation; 2) the role of prolactin in the regulation of
5Alpha-reductase activity in purified rat Leydig cells during sexual
maturation; and 3) the mechanism by which cAMP brings about steroidogenic
desensitization using a newly developed mouse Leydig cell culture system.
This third specific aim will examine the mechanisms by which cAMP causes
decreases in microsomal and mitochondrial P-450 enzyme activities and the
relationship among decreases in microsomal and mitochondrial P-450
activities, substrate depletion and reductions in maximal testosterone
production.  Enzyme activities will be studied using [3H]-labeled steroid
substrates and measuring [3H]-labeled steroid products after extraction and
purification of steroids by thin-layer chromatography.

The proposed studies using the combination of in vivo and in vitro
approaches to study regulation of Leydig cell function will contribute to a
better understanding of the processes that determine maximal testosterone
production at different stages of life and under different pathological
conditions.

## Key facts

- **NIH application ID:** 2196589
- **Project number:** 5R01HD008358-17
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **SAM.gov UEI:** GNJ7BBP73WE9
- **Principal Investigator:** ANITA H PAYNE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1993
- **Award amount:** $212,632
- **Award type:** 5
- **Project period:** 1978-07-01 → 1994-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/2196589

## Citation

> US National Institutes of Health, RePORTER application 2196589, REGULATION OF STEROIDOGENIC ENZYMES IN LEYDIG CELLS (5R01HD008358-17). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/2196589. Licensed CC0.

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