Changes in Cai and pHi during mitosis depend on external Ca++ and Na+.

Eggs were transferred in the different media after fertilization (arrow). Two examples representative of n measurements (number in brackets) are shown in each condition. Variations in pHi (a), evolution of Cai (b) and images of eggs taken 70 min after fertilization (insets in a). A. Transfer in 0Na (1), Am (2) or Ac (3). B. Effect of additional absence of external Ca after transfer in 0Na0Ca (1), Am0Ca (2) or Ac0Ca (3). C. Mean levels of pHi (a) and Cai (b) changes recorded from 60–65 mins after sperm addition in Figs. A and B. pHi changes (a) are expressed relative to that of unfertilized egg (arbitrarily taken as 1) while Cai changes (b) are expressed as the percentage of the fertilization Cai peak arbitrarily taken as 100 (zero is the unfertilized level). Values (means +/− sem) obtained in the absence of external Ca are significantly different (student test, p