Uptake of 3H-catecholamines by rat liver cells occurs mainly through a system which is distinct from uptake1 or uptake2.
Isolated rat hepatocytes were incubated with 200 nmol/l 3H-(-)-noradrenaline or 50 nmol/l 3H-(-)-adrenaline for 15 min, in Krebs-Henseleit solution at 37 degrees C, gassed with 95% O2 5% CO2. Monoamine oxidase and catechol-O-methyl transferase were inhibited with pargyline (500 mumol/l) and Ro 01-2812 (3,5-dinitropyrocatechol; 2 mumol/l), respectively. Total radioactivity present in the cells, which corresponded mostly to intact 3H-amine, was measured. The content of 3H-noradrenaline increased with time of incubation, a plateau having been reached after 15 min of incubation. After 15 min of incubation, the cell: medium ratio for 3H-noradrenaline and 3H-adrenaline was 0.6-0.7. Desipramine (an inhibitor of the neuronal uptake of catecholamines-uptake1; 1 mumol/l) did not affect the uptake of either 3H-noradrenaline or 3H-adrenaline into hepatocytes. Corticosterone (an inhibitor of the extraneuronal uptake of catecholamines-uptake2; 40 mumol/l) slightly inhibited (by 28%) the uptake of 3H-adrenaline, and did not significantly reduce 3H-noradrenaline uptake. Probenecid (an inhibitor of the renal transport of organic anions; 100 mumol/l) did not influence the amount of either 3H-noradrenaline or 3H-adrenaline in hepatocytes. Cyanine 863 (an inhibitor of the renal transport of organic cations; 10 mumol/l) decreased by 62% the uptake of 3H-adrenaline into cells but did not significantly affect 3H-noradrenaline uptake. Bilirubin (a substrate of a hepatic transport for organic anions; 200 mumol/l) produced a significant increase (50%) in the amount of 3H-noradrenaline and 3H-adrenaline present in the cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Martel
F
F
Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal.
Azevedo
I
I
Osswald
W
W
D000818:Animals; D001663:Bilirubin / Q000494:pharmacology; D002395:Catecholamines / Q000378:metabolism*; D003345:Corticosterone / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D066298:In Vitro Techniques; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000378:metabolism; D011339:Probenecid / Q000494:pharmacology; D011806:Quinolinium Compounds / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000494:pharmacology
D002395:Catecholamines; D011806:Quinolinium Compounds; C016855:cyanine 863; D012964:Sodium; D011339:Probenecid; D001663:Bilirubin; D011188:Potassium; D003891:Desipramine; D003345:Corticosterone