Experimental induction and mathematical modeling of dynamics in rat round spermatids.

Cytosolic concentration ([ ]) has an important role in spermatozoa and hence it regulates fertilization. In male germinal cells, there are indirect evidences that this ion could regulate physiological processes in spermatogenesis. Since little is known about homeostasis in spermatogenic cells, in this work we propose a mathematical model that accounts for experimental [ ] dynamics triggered by blockade of the SERCA transport ATPase with thapsigargin in round rat spermatids, without external and with different extracellular lactate concentrations. The model included three homogeneous calcium compartments and ase activities sensitive and insensitive to thapsigargin, and it adjusted satisfactorily the experimental calcium dynamic data. Moreover, an extended version of the model satisfactorily adjusted the stationary states of calcium modulated by extracellular lactate, which is consistent with the participation of a low affinity lactate transporter and further lactate metabolism in these cells. Further studies and modeling would be necessary to shed some light into the relation between -lactate-ATP homeostasis and cell-cell interactions in the seminiferous tubules that are expected to modulate dynamics by hormonal factors or energetic substrates in meiotic and postmeiotic spermatogenic cells.