INTERDOUBLET SLIDING IN BOVINE SPERMATOZOA - ITS RELATIONSHIP TO FLAGELLAR MOTILITY AND THE ACTION OF INHIBITORY AGENTS

Interdoublet sliding rates were assessed in bull sperm, utilizing a fr eeze-thaw procedure to allow axonemal disintegration, The sliding rate at 23 degrees C increased with increasing MgATP concentrations up to 1 mM ATP, to plateau at 8 mu m/sec. The analyzed interdoublet shear in both live and demembranated (Triton X-100-extracted) bull sperm react ivated with 1 mM ATP established maximal microtubule sliding rates at 6 mu m/sec during flagellar beating, Therefore, in vitro sliding rates were sufficient to account for the beat in intact flagella, The effec t of inhibitors of flagellar motility on in vitro sliding rates was ev aluated. While 8 mu M vanadate minimally reduced the sliding rate (to approximate to 4 mu m/sec), only 0.5 mu M vanadade was sufficient to t erminate reactivated bull sperm motility, Nickel ion (0.66 mM terminat ed all spontaneous motility, while only reducing microtubule sliding r ates to approximate to 5.0 mu m/ sec. Exposing intact bull sperm to th eophylline (1 mM), and incubating the subsequently demembranated sperm in cAMP (3 mu M), improved flagellar motility, but had little impact on microtubule sliding rates as determined by axonemal disintegration. Furthermore, deactivating live sperm with 2 mM KCN and 4 mM 2-deoxy-D -glucose renders the subsequently reactivated sperm immotile (as long as exogenous cAMP is absent), Yet, this treatment only reduced the sli ding rate by 38%, Paradoxically, 4 mM MgADP reduced the sliding rates most dramatically (86%), whereas demembranated sperm models retain a s trong, coordinated beating pattern in the presence of MgADP. These res ults demonstrate that there is no direct relationship between interdou blet sliding rates and the capacity for coordinated flagellar beating. (C) 1996 Academic Press, Inc.