Figure 2. Naturally-aged eggs feature a reduced Ca²⁺ influx capacity.

(a) A typical Ca²⁺ response to thapsigargin followed by Ca²⁺ add-back is demonstrated with pseudocoloured time-lapse images, with warmer colours indicating higher [Ca²⁺]_i. Numbers in the top left of each image panel represent minutes (mins). (b) Representative Ca²⁺ response curve in MII eggs from young and naturally-aged mice after treatment with thapsigargin (10 μm) followed by Ca²⁺ (1.7 mM) add-back. The Ca²⁺ add-back response curve has been magnified (grey box outline). (c) Quantitative analyses of the thapsigargin response in young (n = 18) and aged (n = 10) eggs. Area under the curve (AUC) and fold-change fluorescence ratio calculations revealed maternal age does not affect thapsigargin-sensitive [Ca²⁺]_ER stores (P = 0.11 and P = 0.34, respectively). (d) Quantitative analyses of the Ca²⁺ -add back response in young (n = 17) and aged (n = 10) eggs. AUC and fold-change fluorescence calculations showed Ca²⁺ influx capacity is reduced with maternal age (P = 0.0009 and P = 0.0002, respectively). Experiments performed in Ca²⁺ -free media. ns indicates not statistically significant. a.u. represents arbitrary units. Error bars are s.e.m.