INTRACELLULAR PH REGULATION IN RAT ROUND SPERMATIDS

Intracellular pH has been shown to be an important physiological param eter in cell cycle control and differentiation, aspects that are centr al to the spermatogenic process. However, the pH regulatory mechanisms in spermatogenic cells have not been systematically explored. In this work, measuring intracellular pH (pH(i)) with a fluorescent probe (BC ECF), membrane potential with a fluorescent lipophilic anion (bisoxono l), and net movement of acid using a pH-stat system, we have found tha t rat round spermatids regulate pH(i) by means of a V-type H+-ATPase, a HCO3- entry pathway, a Na+/HCO3- dependent transport system, and a p utative proton conductive pathway. Rat spermatids do not have function al base extruder transport systems. These pH regulatory characteristic s seem specially designed to withstand acid challenges, and can genera te sustained alkalinization upon acid exit stimulation.