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Published on: July 29, 2021
Evidence for nitrite reductase activity in intact mouse Leydig tumor cells
1Department of Chemical Pathology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR, PR China. nspanesar@cuhk.edu.hk
Steroids
|September 6, 2006
Summary
This study reveals a novel pathway for nitric oxide (NO) production in Leydig cells, independent of the L-arginine-NO synthase (NOS) pathway. Mitochondrial respiratory chain complexes (MRCC) facilitate NO generation from nitrite, impacting testosterone production.
Area of Science:
- Biochemistry
- Endocrinology
- Cell Biology
Background:
- Nitric oxide (NO) is implicated in inhibiting steroidogenesis via the L-arginine-NO synthase (NOS) pathway.
- Nitrite and nitrate ions also inhibit steroidogenesis through an unelucidated NO-dependent mechanism.
- A recent report suggests mitochondrial respiratory chain complexes (MRCC) possess nitrite reductase activity.
Purpose of the Study:
- To investigate the role of MRCC inhibitors in modulating testosterone production in mouse Leydig tumor cells (MLTC-1).
- To explore the potential involvement of a non-L-arginine-NOS pathway in NO-mediated steroidogenesis regulation.
- To determine the effect of human chorionic gonadotropin (hCG) on nitrate uptake and NO production in MLTC-1.
Main Methods:
- MLTC-1 cells were treated with MRCC inhibitors (antimycin A, myxothiazol, rotenone, thenoyltrifluoroacetone) under basal and hCG-stimulated conditions.
- Testosterone and cyclic AMP (cAMP) production were measured.
- NO production from nitrite was assessed.
- Expression of NOS isoforms (mRNA) was analyzed.
- Nitrate uptake was quantified.
Main Results:
- MRCC inhibitors differentially affected testosterone production in stimulated MLTC-1 cells, with complex III inhibitors showing the greatest effect.
- In unstimulated cells, MRCC inhibitors increased basal testosterone production, inversely correlating with NO production inhibition.
- The L-arginine-NOS pathway did not influence basal testosterone production in MLTC-1 or primary Leydig cells, despite the presence of eNOS and nNOS mRNA.
- hCG stimulation enhanced nitrate uptake into MLTC-1 cells.
Conclusions:
- Mouse Leydig tumor cells (MLTC-1) possess a functional nitrite reductase activity linked to mitochondrial respiratory chain complexes (MRCC).
- The L-arginine-NO synthase (NOS) pathway appears dormant in regulating basal testosterone production in MLTC-1.
- Nitrite and nitrate ions, potentially facilitated by hCG-mediated nitrate uptake, represent an alternative NO source influencing steroidogenesis in Leydig cells.
