Induction of cystathionase in human fetal liver explants

Previous studies have shown that cystathionase activity is virtually absent from human fetal liver and develops some time after birth. In the present study we describe the in vitro effects of dibutyryl cyclic AMP(dBcAMP), glucagon and dexamethasone on the activity of cystathionase in human fetal liver. Human fetal liver explants (gestational age 10 to 20 weeks) incubated in organ culture for 1-3 days contained only trace amounts of cystathionase activity. Incubation of liver explants for 24 hours with dBcAMP (0.2mM) in the presence of theophylline (0.5mM) increased the activity of cystathionase to adult human levels (104-198 nmoles cysteine/mg protein/h). Incubations in the presence of glucagon (150ug/ml) or dexamethasone (20ug/ml) also increased the cystathionase activity of the liver explants to the similar levels. The increase in cystathionase activity was inhibited by simultaneous incubation with cycloheximide or actinomycin D. These experiments show that cystathionase activity can be induced in human liver in vitro.