Non-specific currents at fertilisation in sea urchin oocytes.

Using the whole-cell voltage-clamp technique to clamp sea urchin oocytes we show that the fertilising spermatozoon triggers an inward current of -521 +/- 56.7 pA (n = 8) at activation. Simultaneously, the plasma membrane depolarises and the conductance increases from 23.4 +/- 1.4 to 40.6 +/- 1.2 nS (n = 8). The I/V curve for the peak activation current is linear and the current reverses between 0 and +20 mV, suggesting a non-specific ion current. Since injection of inositol triphosphate induced an inward current of -1062 +/- 314 pA (n = 4), and the current was inhibited by preloading oocytes with the calcium chelator BAPTA, the non-specific activation current in sea urchin appears to be calcium dependent.