Patrini C, Reggiani C, Laforenza U, Rindi G
Institute of Human Physiology, University of Pavia, Italy.
Alcohol Alcohol. 1988;23(6):455-63.
The effect of ethanol (4.7 g/kg body wt intragastrically as a single dose or once daily for 35 days) on the transport of thiamine from plasma to four brain regions (cerebellum, cerebral cortex, pons and medulla) was studied in albino rats. Animals were given an intravenous injection of labelled thiamine with a sampling procedure which allowed the determination of regional blood flow and tissue thiamine uptake. Regional blood flow was found to be enhanced after acute, but non chronic, ethanol administration. The magnitude of increase ranged from 13 to 35% depending on the brain region being considered. Thiamine was transferred from plasma to cerebral tissue by a saturable process with a non-saturable component prevailing at thiamine concentrations above 10-15 microM. Three main modifications in the thiamine transport were found as a result of ethanol treatment: a reduction in affinity for the carrier (Km increased), an increase in maximal transport rate (Jmax) and an increase in non-saturable diffusion (KD constant increased). The effects were more pronounced after acute ethanol administration. As a consequence of these modifications both acute and chronic ethanol treatment caused an increase in thiamine transport rate at high plasma concentrations. On the contrary, at low (physiological) plasma concentrations, thiamine transport was little increased by acute ethanol administration and virtually unaffected by chronic ethanol intoxication.
在白化大鼠中研究了乙醇（单次灌胃剂量为4.7 g/kg体重或连续35天每天一次）对硫胺从血浆转运至四个脑区（小脑、大脑皮层、脑桥和延髓）的影响。给动物静脉注射标记的硫胺，并采用一种采样程序来测定局部血流量和组织对硫胺的摄取。发现急性而非慢性给予乙醇后局部血流量增加。增加幅度在13%至35%之间，具体取决于所考虑的脑区。硫胺通过一个可饱和过程从血浆转运至脑组织，在硫胺浓度高于10 - 15 microM时，非饱和成分占主导。乙醇处理导致硫胺转运出现三个主要变化：对载体的亲和力降低（Km增加）、最大转运速率（Jmax）增加以及非饱和扩散增加（KD常数增加）。急性给予乙醇后这些影响更为明显。由于这些变化，急性和慢性乙醇处理均导致高血浆浓度下硫胺转运速率增加。相反，在低（生理）血浆浓度下，急性给予乙醇对硫胺转运的增加作用很小，而慢性乙醇中毒对其几乎没有影响。
