The roles of Ca and Mg in starfish oocyte maturation induced by 1-methyladenine

✍ Scribed by Rosenberg, Michael P. ;Lee, Harold H.

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 675 KB
• Volume: 217
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402170309

✦ Synopsis

Abstract

The ovarian hormone 1‐methyladenine (1‐MA) stimulates fully grown starfish oocytes to undergo germinal vesicle breakdown (GVB). Patiria miniata oocytes treated with 10^−6^ M 1‐MA underwent GVB by 45 minutes of treatment. However, in the absence of extracellular Ca^++^ GVB was delayed, with maximum GVB occuring at 180 minutes of treatment. Both the rate and amount of^3^ H‐1‐MA bound were depressed in the absence of extracellular Ca^++^ Reflecting this decrease in hormone binding, the minimum time oocytes in CaFSW needed to be exposed to the hormone was increased from 12 to 35 minutes. Direct measurement of total cellular Ca concentrations during 1‐MA‐induced maturation revealed an increase in Ca levels by 30 minutes posttreatment, followed by a decrease to initial level by 60 minutes. In the absence of extracellular Mg^++^, oocytes treated with 1‐MA did not undergo GVB. However, binding of the hormone was not dependent on extracellular Mg^++^. Total cellular Mg concentrations were found to increase to maximum levels by 10 minutes of hormone treatment, and to decrease to basal levels after 30 minutes. Our data suggest that free‐diffusable Mg^++^ was necessary for hormone action during the critical hormone‐dependent period, while extracellular Ca^++^ was important for hormone binding. Furthermore, we interpret our data to indicate that 1‐MA regulates oocyte permeability to Ca and Mg during oocyte maturation.