Hormonal modulation of amino acid transport in rat hepatoma cells in tissue culture.

摘要: Abstract 1. HTC cells in suspension culture actively transport the model amino acid α-aminoisobutyric (AIB) by a saturable, energy-dependent process that demonstrates Michaelis-Menten kinetics. 2. Dexamethasone markedly decreases AIB transport, reducing uptake 75% within 2 hours and 85% after 18 to 24 incubation with hormone. has no effect on for 30 min, which initial velocity of declines exponentially. The is half-maximal 1 hour. After exposure dexamethasone, Vmax 25% control value, while Km essentially unchanged. hours, further 20% increases three times value. influx into does not increase efflux from cells. 3. Insulin only slightly untreated In contrast, previously incubated insulin uptake. dexamethasone then 5-fold apparent min maximal hours; it declined 4 hours. insulin, nearly 70% times. 4. Both hormonal effects are dependent protein synthesis, cycloheximide added prior either hormone completely blocks its effect. Addition actinomycin D partially