ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Electropotential differences between the cytoplasm and external medium have been compared in the mature R. pipiens occyte and the ovulated unfertilized egg as a function of [Na]o, [K]o, [Ca]o and [Cl]o. In solutions containing 1.0 mM Ca++ the oocyte behaved as though it were predominantly permeable to K+ and Cl-, i.e., like a KCl electrode. However, the steady potential decreased with decreasing [Ca]o and in 5 × 10-4 mM [Ca]o the oocyte membrane behaved like a NaCl electrode. Studies on the steady potential as a function of [Na]o, [K]o and [Cl]o in 1.0 mM Ca++ or Ca-free solutions suggest that Ca++ controls the passive permeability of the oocyte membrane to Na+ and Cl-. In the ovulated unfertilized egg the K+ selectivity of the cell membrane disappeared and the system behaved like a NaCl electrode. No effect of external Ca++ or K+ concentration changes on the steady potential was observed. These results indicate that the ion permeability properties of the ovulated egg are similar to that of the ovarian oocyte in Ca-deficient medium, and suggests that the mechanism of ovulation may involve the removal of Ca++ regulation of ion permeability of the egg cell membrane.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040670303
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