Tracer-flux analysis of sodium and potassium permeability in differentiating mouse spermatozoa.

to differentiation of the spermatozoon to the mature motile condition. During differentiation, striking variations occur not only in cell shape but also in the ionic composition of the developing spermatozoa and their surrounding media, specifically in the ratio of sodium to potassium (Cragle, Salisbury & Muntz, 1958). The membrane potential (Em) of cells isolated from mouse testis is dependent on both sodium and potassium concentration gradients (McGrady, 1979). Cuthbert & Wong (1975) postulated a relatively high permeability ratio of sodium to potassium (PNa/PK) based on their study of membrane potential in rat seminiferous tubules. Wong (1976) studied uptake of 22Na into rat seminiferous tubules and found that entry of sodium occurs rapidly and by simple diffusion. Chueng, Hwang & Wong (1976, 1978) showed a significant contribution of sodium as well as potassium to membrane potential of rat epididymal epithelial cells. Zimmerman et al (1979) studied the uptake of Na+ and K+ in boar epididymal spermatozoa and suggested that caput cells