Uptake of dopamine by rat hepatocytes in vitro
Zhong, Z.D.; Wattiaux-de Coninck, S.; Wattiaux, R.
Zhongguo Yao Li Xue Bao 15(4): 289-294
1994
ISSN/ISBN: 0253-9756 PMID: 7801765 Document Number: 423095
The present results showed that uptake of dopamine (DA) by rat isolated hepatocytes was mediated, in addition to simple diffusion, mainly by a transporter-involved process, with K-m of 66.8 mu-mol and V-max of 52.3 pmol cntdot min-1/10-5 cells. The process was pH- and temperature-dependent and required an activation energy of 4.12 kcal cntdot mol-1(Q-10 = 1. 25) in the range of 2.0 - 12.7 degree C and 13.0 kcal cntdot mol-1 (Q-10 = 2.0) in the range of 12.7 39.0 degree C. Cysteine residue having free thiol group was unrelated to the activity of the transporter. Catecholamines, serotonin, and cocaine inhibited the DA transport, but tyramine (TA) and tryptamine, as well as benztropine and imipramine (which are potent inhibitors for hepatic TA transporter and neuronal DA transporter), had no inhibitory effect on the transport of DA in these cells. These results indicated that DA was taken up into hepatocytes by a distinct carrier. NaF and mastoparan influenced the transport activity in these cells further, suggesting that signal transducing G-proteins may be involved in the regulation of DA transporter in rat hepatocytes.