INTRACELLULAR SIGNAL-TRANSDUCTION MECHANISMS OF RAT EPIDIDYMAL SPERMATOZOA AND THEIR RELATIONSHIP TO MOTILITY AND METABOLISM

The role of intracellular signal transduction mechanisms in regulating the motility and metabolism of rat spermatozoa in undiluted caudal ep ididymal fluid (CEF) was examined. Samples of CEF containing immotile spermatozoa were exposed to drugs and other agents that either stimula te signal transduction pathways or mimic the action of their second me ssengers. Under these conditions, sperm motility in 25-30 nl of CEF wa s stimulated by calcium ions (Ca2+), N-2,2'-O-dibutyrylguanosine 3':5' -cyclic monophosphate (dibutyryl cGMP), cyclic adenosine 3':5'-monopho sphate (cAMP), N-6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (dibutyryl cAMP), 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo cAMP), caffeine, theophylline and bicarbonate ions (HCO3-). Other age nts such as magnesium ions (Mg2+), veratridine, phospholipase C (PLC), ionophore A23187, 1,2-dioctenoyl-sn-glycerol (DAG), phorbol 12-myrist ate 13-acetate, phospholipase A(2) (PLA(2)), arachidonic acid, and mel ittin did not significantly influence motility. In the presence of rad iolabelled energy substrates, untreated (immotile) spermatozoa in samp les of CEF utilised D-U-C-14glucose and 1-C-14acetate as exogenous energy sources for oxidative metabolism. No detectable C-14-lactate w as produced, and none of the drugs altered the rate of glycolytic or o xidative metabolism. The findings suggest that the motility of rat cau dal epididymal spermatozoa is regulated by Ca2+ and the guanylate cycl ase and adenylate cyclase pathways, but not through the PLC and PLA(2) pathways. Also, their metabolism of exogenous substrate was uncoupled from the induction of motility, and their oxidative capacity exceeded the rate of flux of glucose-carbon through the glycolytic pathway. (C ) 1994 Wiley-Liss, Inc.