Regulation of fowl sperm motility: Evidence for the indirect, but not direct, involvement of dynein-ATPase activity on the reversible temperature-dependent immobilization

Potential mechanisms of the reversible temperature-dependent immobilization of fowl sperm were investigated. At 30 degrees C, motility of demembranated fowl sperm was inhibited by adding 2 mM ethylene glycol-bis (2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA), but restored immediately after the subsequent addition of 2 mM CaCl2, whereas at 40 degrees C, such additions did not appreciably affect motility (which remained almost negligible). With intact sperm, 10(-9) to 10(-3) M Ca2+ had no effect on motility at 30 degrees C, which remained high. In contrast, intact sperm at 40 degrees C were almost immotile below 10(-5) M Ca2+, and then gradually recovered motility at higher Ca2+ concentrations. The negligible motility of demembranated sperm at 40 degrees C, and at 30 degrees C in the presence of EGTA, was stimulated by addition of 100 nM of the protein phosphatase inhibitor calyculin A. Dynein-ATPase activities of sperm at 40 degrees C in the presence of 2 mM EGTA, 2 mu M CaCl2, 2 mM CaCl2, or 100 nM calyculin A were higher than those at 30 degrees C. Therefore, stimulation of fowl sperm motility by temperature, Ca2+, and phosphatase inhibition was not simply associated with an increase of flagellar dynein-ATPase activity. Furthermore, Ca2+ was essential, at the axonemal level, for initiation of the 'intrinsic' motility of fowl sperm at 30 degrees C, but this Ca2+-dependent mechanism might be different from that involved in restoration of motility of intact sperm at 40 degrees C. In addition, perhaps inhibition of protein phosphatase activity was involved in initiation of sperm motility, but acting at a location different from Ca2+ on the axoneme. (c) 2013 Elsevier Inc. All rights reserved.