IONIC BALANCE OF SPERM CELLS 57 



except perhaps under the highly abnormal condition of sea water 

 made half molar in KC1. 



The general picture is that the head-midpiece fraction is a highly 

 selective ion concentrating mechanism for K in normal sea water. 

 The same system can exclude Na and CI and, when sufficiently high 

 externally, K as well. 



So far as sperm are concerned we would offer the following tenta- 

 tive conclusions: 



1. Sperm, as with all other cells studied, concentrate K and ex- 

 clude CI and Na as compared to normal sea water or blood. 



2. Ion gradient mechanisms depend on activation of head-mid- 

 piece portions of sperm. Separated tails have no power to maintain 

 ion gradients. 



3. Maintenance of normal conducted flagellar movement depends 

 on ion gradients pumped into the tail by the head-midpiece ma- 

 chinery. 



We suggest these findings may have relevance to various aspects of 

 the preservation of sperm and initiation of motility, to be discussed 

 later in this symposium. Sperm collected proximally in the mamma- 

 lian tract are not motile and are in a high K (low gradient) environ- 

 ment. 



On ejaculation, sperm are motile or become motile on exposure to 

 low K-high Na environments which must set up high ion gradients. 

 Isolated sperm tails can still be caused to contract but they do not 

 undulate gracefully in a conducted fashion. 



REFERENCES 



Steinbach, H. B., and P. B. Dunham. 1961. Ionic gradients in some in- 

 vertebrate spermatozoa. Biol. Bull., 120, 411-419. 



