Effects of cytoskeletal inhibitors on water proton relaxation time changes in unfertilized and fertilized sea urchin eggs.

Unfertilized and fertilized sea urchin eggs were used for pulsed proton NMR spin-lattice relaxation time (T1) measurements of cellular water. An 81% increase in T1 time at fertilization was largely explained by the accumulation of extracellular water in the perivitelline space. To assess the role of microtubule and actin filament assembly and disassembly, eggs were treated with drugs that are known to change these cytoskeletal elements (i.e., colchicine, taxol and cytochalasin B). Egg volume was also monitored in all studies to rule out the influence of water content changes on the observed T1 relaxation time changes. Neither assembly nor disassembly of microtubules changed the T1 relaxation time. The role of actin polymerization and depolymerization is discussed as a possible explanation for the observed cell cycle dependent water proton T1 relaxation time changes.