ISSN:
1432-1912
Keywords:
Hepatocyte
;
Catecholamines
;
Uptake1
;
Uptake2
;
Renal organic cation transport
;
Bilirubin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract 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°C, gassed with 95% O2 5010 CO2. Monoamine oxidase and catechol-O-methyl transferase were inhibited withpargyline (500 μmol/l)and Ro 01-2812 (3,5-dinitropyrocatechol; 2 μol/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 — uptake,; 1 μmol/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 μmol/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 μmol/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 μmol/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 μol/l) produced a significant increase (50%) in the amount of 3H-noradrenaline and 3H-adrenaline present in the cells. When isolated hepatocytes were incubated in a sodium-free medium (sodium being replaced by choline or lithium) there was a very marked inhibition of 3H-noradrenaline and 3H-adrenaline uptake (by 85–97%). An increase in potassium content of the medium (from 6.6 to 50 mmol/l) did not affect the uptake of either 3H-amine into isolated cells. In conclusion, the uptake of catecholamines by isolated liver cells possesses characteristics that distinguish it from the classic uptake systems for catecholamines (uptake1 and uptake2): (1) it is sodium-dependent but not affected by desipramine; (2) it is only slightly sensitive to corticosterone and not affected by potassium-induced depolarization; (3) it is partially sensitive to cyanine 863. Moreover, the increase of 3H-amine content in the cells in the presence of bilirubin suggests the possibility of catecholamines being excreted from the hepatocytes through the bilirubin transporter. PhD student with a grant from JNICT (Programa Ciência)
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00241086
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