Effects of X-irradiation on the calcium channel of the mouse oocyte.
Effects of a single whole-body X-irradiation (0.2-100 Gy) were studied on Ca2+ channels in mature mouse oocytes using the two-electrode voltage-clamp method. No significant changes were observed in the electrophysiological properties of oocytes when the dose of X-rays was smaller than 10 Gy. However, the following changes, dependent on the dose of X-rays and on the time after irradiation, were observed with higher doses. 1) The resting potential and the input resistance of the oocyte were slightly reduced. 2) Inward Ca2+ current was reduced in amplitude but the shape of the I-V (current-to-voltage) relations were preserved. 3) Both the activation and the inactivation processes of the Ca2+ current became slower. These changes in the kinetics of the Ca2+ channel were observed even when no appreciable change was detected in the amplitude of the Ca2+ current. 4) The steady-state inactivation curve of the Ca2+ current was shifted in a depolarizing direction and the slope of the curve became steeper. These data indicate that high doses of X-rays can affect Ca2+ channels in mouse oocytes and that the kinetics of the Ca2+ channel are more susceptible to irradiation than the amplitude of the Ca2+ current.
Yoshida
S
S
Department of Physiology, Nagasaki University School of Medicine, Japan.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology / Q000528:radiation effects*; D005260:Female; D008564:Membrane Potentials / Q000528:radiation effects; D051379:Mice; D008813:Mice, Inbred ICR; D009865:Oocytes / Q000502:physiology / Q000528:radiation effects*; D012964:Sodium / Q000378:metabolism; D015222:Sodium Channels / Q000502:physiology / Q000528:radiation effects; D014965:X-Rays
D015220:Calcium Channels; D015222:Sodium Channels; D012964:Sodium; D002118:Calcium