AMP-activated protein kinase negatively regulates heat treatment-induced lactate secretion in cultured boar sertoli cells

Abstract

Lactate secreted by Sertoli cells plays an important role in spermatogenesis. Heat stress changes AMP-activated protein kinase (AMPK) activity in many tissues and cells, and enhances lactate secretion in Sertoli cells. However, it is unclear whether heat stress affects lactate secretion by regulating the phosphorylation level of AMPK in boar immature Sertoli cells. In this study, immature boar Sertoli cells were treated at 43 °C for 30 min in an incubator. From 0 to 48 h post-heat stress, lactate secretion was enhanced and reached the maximum level (175% of the control) at 12 h. However, with increased recovery time, the phosphorylation level of AMPK decreased gradually, and reached the minimum level (58% of the control) at 12 h. Compared with heat treatment alone, pretreatment with the AMPK agonist AICAR (2 mmol/L, 2 h) reduced lactate secretion by 42.6%. Additionally, AICAR significantly decreased the lactate dehydrogenase (LDH) activity, and the mRNA and protein expression levels of GLUT3, LDHA, and MCT1. In addition, AMPK overexpression reduced lactate secretion by 22.5%, significantly decreased the LDH activity, and mRNA and protein expression levels of GLUT3, LDHA, and MCT1. These results showed that AMPK reduces heat-induced lactate secretion by decreasing the expression levels of GLUT3, LDHA and MCT1. The results also suggested that AMPK is a negative regulator of heat treatment-induced lactate secretion in cultured boar Sertoli cells.