Energy metabolism and its linkage to intracellular Ca²⁺ and pH regulation in rat spermatogenic cells

Energy metabolism and intracellular adenine nucleotides of meiotic and postmeiotic spermatogenic cells are highly dependent on external substrates for oxidative phosphorylation and glycolysis. Using fluorescent probes to measure the changes in cytosolic [Ca²⁺] ([Ca²⁺](i)) and pH (pH(i)), we were able to demonstrate that changes in energy metabolism of meiotic and postmeiotic spermatogenic cells were rapidly translated into changes of pH(i) and [Ca²⁺](i) in the absence or presence of external Ca²⁺. Under these conditions, mitochondria were gaining cytosolic calcium in these cells. Our results indicate that Ca²⁺ mobilised by changes in metabolic energy pathways originated in thapsigargin-sensitive intracellular Ca²⁺ stores. Changes in intracellular adenine nucleotides, measured by HPLC, and a likely colocalization of ATP-producing and ATP-consuming processes in the cells seemed to provide the linkage between metabolic fluxes and the changes in pH(i) and [Ca²⁺](i) in pachytene spermatocytes and round spermatids. Glucose metabolism produced an increase of [Ca²⁺](i) in round spermatids but not in pachytene spermatocytes, and a decrease in pH(i) in both cell types. Hence, glucose emerges as a molecule that can differentially modulate [Ca²⁺](i) and pH(i) in pachytene spermatocytes and round spermatids in rats. (C) 2000 Editions scientifiques et medicales Elsevier SAS.