VII. Decrease in the Rate of Respiration in the Spermatozoa of the Sea Urchin, Hemicentrotus Pulcherrimus, Caused by Long Chain Fatty Acyl-CoA-induced Inhibition of the Movement

Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus , showed marked decrease in respiration, and arrested movement after interaction with the fixed eggs. Immotile spermatozoa that had reacted with fixed eggs contained higher levels of long chain fatty acyl-CoAs than normal motile spermatozoa. On treatment with carnitine, the immotile spermatozoa became motile again and their intracellular concentrations of long chain fatty acyl-CoAs decreased. On incubation with anti-mycin A or CN^? for 20 min, the motility of normal spermatozoa decreased gradually but their long chain fatty acyl-CoA content changed only slightly. The decrease in sperm motility in the latter case was probably due to decrease in the level of ATP, resulting from inhibition of respiration by antimycin A or CN^?. The motility of spermatozoa extracted with Triton X-100 was restored by ATP and their movement was inhibited by long chain fatty acyl-CoAs, such as myristoly CoA and palmitoyl-CoA, but was not by short chain fatty acyl-CoAs, such as acetyl-CoA, propionyl CoA and butyryl-CoA. Na-palmitate, Na-myristate and CoA did not inhibit the reactivation of extracted spermatozoa by ATP.