Abstract
Few data have suggested how norepinephrine (NE) and acetylcholine (Ach) regulate the development of Leydig cells in mice at prepuberty, except for data indicating endocrine effects. The present study aims to elucidate the roles of NE and Ach on the differentiation and proliferation of Leydig cells. Firstly, the expression of adrenergic receptors and muscarinic acetylcholine receptors in Leydig cells was investigated. It was found that adrenergic receptors (β1AR, β2AR, and α1D) and muscarinic acetylcholine receptors (M1 and M3) mRNA are expressed in adult Leydig cells. Then, the effects of NE and Ach on the differentiation and proliferation of Leydig cells were analyzed. The results showed that NE and Ach at 10 μM significantly increased the number of 3β-hydroxysteroid-dehydrogenase- (3β-HSD-) positive Leydig cells and improved the expression of proliferating cell nuclear antigen (PCNA) in Leydig cells on postnatal day (PD) 15 (P < 0.05). NE and Ach at 10 μM had no impact on the expression of PCNA mRNA (P > 0.05), but reduced the expression of 3β-HSD mRNA in adult Leydig cells and a murine Leydig tumor cell line (MLTC-1) (P < 0.05). Therefore, a conclusion may be reached that NE and Ach participated in stimulating the development of Leydig cells in mice from prepuberty to adult stage.
Highlights
It has been generally acknowledged that Leydig cells play a key role in synthesizing testosterone and regulating the spermatogenesis
The cells isolated from the postnatal day (PD) 50 mice were adult Leydig cells, and the purity of the Leydig cells examined by histochemical staining for 3β-HSD using 1 mg/mL etiocholanolone as the enzyme substrate was observed to be 85%
RTPCR results showed that β1AR, β2AR, and α1D receptors mRNA were expressed in adult Leydig cells, especially the β2AR and α1D receptor mRNA (Figure 1). β3AR and α1A receptors mRNA were not detected in the adult Leydig cells
Summary
It has been generally acknowledged that Leydig cells play a key role in synthesizing testosterone and regulating the spermatogenesis. The final population of Leydig cells in the adult testis is established depending on the proliferation and differentiation of Leydig cells at prepuberty and develops to the adult population of Leydig cells [1, 2]. Compared with the endocrine effects, previous data seldom demonstrate the effects of norepinephrine (NE) and acetylcholine (Ach) on the development of Leydig cells through their receptors. The expression of adrenergic and muscarinic acetylcholine receptors in testicular Leydig cells has been unclear. It was indicated in some studies that catecholamine was capable of stimulating the secretion of testosterone through both alpha- and beta-adrenergic receptors in the immature testis of the golden hamster [8]. Carbachol, a cholinergic agonist, is capable of inhibiting the secretion of testosterone via purified rat Leydig cells [9, 10]
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