Abstract
The stress-induced initiation of proapoptotic signaling in Leydig cells is relatively well defined, but the duration of this signaling and the mechanism(s) involved in opposing the stress responses have not been addressed. In this study, immobilization stress (IMO) was applied for 2 h daily, and animals were euthanized immediately after the first (IMO1), second (IMO2), and 10th (IMO10) sessions. In IMO1 and IMO2 rats, serum corticosterone and adrenaline were elevated, whereas serum androgens and mRNA transcription of insulin-like factor-3 in Leydig cells were inhibited. Reduced oxygen consumption and the mitochondrial membrane potential coupled with a leak of cytochrome c from mitochondria and increased caspase-9 expression, caspase-3 activity, and number of apoptotic Leydig cells was also observed. Corticosterone and adrenaline were also elevated in IMO10 rats but were accompanied with a partial recovery of androgen secretion and normalization of insulin-like factor-3 transcription coupled with increased cytochrome c expression, abolition of proapoptotic signaling, and normalization of the apoptotic events. Blockade of intratesticular glucocorticoid receptors diminished proapoptotic effects without affecting antiapoptotic effects, whereas blockade of intratesticular α(1)-adrenergic receptors diminished the antiapoptotic effects without affecting proapoptotic effects. These results confirmed a critical role of glucocorticoids in mitochondria-dependent apoptosis and showed for the first time the relevance of stress-induced upregulation of α(1)-adrenergic receptor expression in cell apoptotic resistance to repetitive IMOs. The opposite role of two hormones in control of the apoptotic rate in Leydig cells also provides a rationale for a partial recovery of androgen production in chronically stressed animals.