Fig. 5. Effects of glycolytic inhibitor iodoactetate (IAA; 0.4 mmol l^-1) on immature male (A) and female (B) cardiac tissue. After a 15 min incubation with IAA, ventricle strips were exposed to either increased Ca²⁺ (5 mmol l^-1), testosterone (T; 0.3 µmol l^-1), 17ß-estradiol (E2; 1 nmol l^-1) or epinephrine (Epi; 1 µmol l^-1). Plus (+) and minus (-) denote presence and absence, respectively, of specific compounds in the incubation medium. For immature males and females, elevated Ca²⁺ or Epi, but not sex steroids, increased twitch force when glucose (5 mmol l^-1) was present. ^*P<0.05. Values are means ± s.e.m. (N=9-11 strips per group).