Fig. 3. Heart laterality in embryos treated with Ca_i²⁺ antagonists. The indicated agents were implanted to the left or right of Hensen's node at HH3++/4; heart laterality was scored 20 hours later. The percentage of embryos with a right-looped (R, situs solitus) or left-looped (L, situs inversus) heart is shown; the number of embryos per treatment is indicated in parentheses. Treatments were: DMSO carrier solvent, Bapta-AM (30 mM), ionomycin (1 mM), U73122 (10 mM), EGTA (5 mM), ryanodine (2.5 mM), ryanodine (2.5 mM) plus EGTA (5 mM), and calmidizolium (5 µM). Asterisks indicate situs inversus frequencies that significantly differ from controls by ² analysis (P<0.05).