Effects of gamma radiation on luteinizing hormone (LH) receptor expression, signal transduction and steroidogenesis in cultured rat Leydig cells.
OBJECTIVE
To investigate the dose-dependent effects of gamma radiation on rat Leydig cell luteinizing hormone (LH) receptor expression, signal transduction and steroidogenesis.


METHODS
Leydig cells isolated from testicles of adult male albino rats were cultured and exposed to different doses (2, 4, 6, 8 and 10 Gy) of fractioned gamma radiation for three days. Normal as well as irradiated cells were used for the quantification of cell surface LH receptor or LH/cyclic adenosine monophosphate (cAMP) stimulation test or total ribonucleic acid (RNA) isolation to study the LH receptor messenger RNA (mRNA) expression by reverse transcriptase polymerase chain reaction (RT-PCR).


RESULTS
Radiation was found to have dose-dependent effects on rat Leydig cell surface LH receptor, basal and LH-stimulated cAMP production, basal, LH and cAMP-stimulated steroidogenesis. Lower doses (2 and 4 Gy) of radiation did not induce any change, whereas higher doses (6, 8 and 10 Gy) of radiation exposure diminished the above said parameters significantly. In spite of the low level of cell surface LH receptors following higher doses of radiation exposure, its mRNA level was not altered under any dose level.


CONCLUSIONS
From these observations, it is concluded that gamma radiation has dose-dependent inhibitory effects on Leydig cell LH signal transduction and steroidogenesis. Decreased cell surface LH receptor following higher doses of radiation exposure is not coupled with altered LH receptor mRNA level.
Sivakumar
R
R
Department of Endocrinology, Dr. ALM PG Institute of Basic Medical Sciences, University of Madras, Taramani, Chennai--600 113, India.
Balasubramanian
K
K
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays; D005786:Gene Expression Regulation / Q000502:physiology / Q000528:radiation effects; D007985:Leydig Cells / Q000166:cytology / Q000502:physiology* / Q000528:radiation effects*; D008297:Male; D011829:Radiation Dosage; D051381:Rats; D017208:Rats, Wistar; D011974:Receptors, LH / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology* / Q000528:radiation effects; D013256:Steroids / Q000096:biosynthesis*
D011974:Receptors, LH; D013256:Steroids