Glucocorticoid Regulation of Amino Acid Transport inAnucleate Rat Hepatoma (HTC) Cells

The transportofa-aminoisobutyricacid(AIB)by rathepatoma tissueculture(HTC) cellsisrapidlyand reversiblyinhibitedby dexamethasone and other glucocorticoids . To investigatethe roleof the nucleus inthe regulationof transportand todetermine whether steroidhormones or steroid-receptorcomplexes may have directeffectson cytoplasmicor membrane functions,we have examined the regulationof transportby dexamethasone in anucleateHTC cells.Cytoplastsprepared from suspensionculturesof HTC cellsfullyretain activetransportofAIB with thesame kineticpropertiesas intactcells.However, theuptake of AIB isnot inhibitedby dexamethasone orothercorticosteroids .Neitheristheinhibitedrateof transport,manifested by cytoplastsprepared from dexamethasone-treated cells,restoredto normal upon removal of the hormone .Anucleate cellsexhibitspecific,saturablebindingof (3H)dexamethasone ;however, the bindingisreduced compared with thatof intactcells.The nucleusisthusrequiredfortheglucocorticoidregulationofamino acidtransportinHTC cells.