Hakvoort A, Haselbach M, Galla H J
Institut für Biochemie, Westfälische Wilhelms-Universität, Wilhelm-Klemm-Strasse 2, D-48149 Münster, Germany.
Brain Res. 1998 Jun 8;795(1-2):247-56. doi: 10.1016/s0006-8993(98)00284-4.
We have investigated the transport properties of cultured porcine choroid plexus cells grown on permeable membranes and in serum-free medium. Withdrawal of serum yielded cell cultures with permeabilities low enough to establish and maintain a pH-gradient between the two compartments of the filter system and to allow apical fluid secretion. This became possible because of ten-fold increased electrical resistance of 1700 Omega cm2 in the absence of serum. These plexus epithelial cells transported phenol red, fluorescein, riboflavin and penicillin G from the apical to the basolateral side. KM values and vmax were determined and come close to in vivo values. Competitive inhibition with probenicid showed that the organic anion transporter is involved. Riboflavin transport however was not completely inhibited and did not respond quantitatively to the stilben derivate SITS that blocks the Cl-/HCO3--exchanger. We assume that an additional transport system exists for riboflavin. Ascorbic acid and myo-inositol were transported from the basolateral to the apical side in vitro which strongly resembles the in vivo transport from the blood to the cerebrospinal fluid. Again the experimental in vitro KM values come close to the in vivo values. The established epithelial cell culture model thus closely mimics the blood-CSF-barrier and may be a useful tool to further elucidate transport to and from the brain.
我们研究了在可渗透膜上且在无血清培养基中生长的培养猪脉络丛细胞的转运特性。去除血清后得到的细胞培养物，其通透性足够低，能够在过滤系统的两个隔室之间建立并维持pH梯度，并允许顶端液体分泌。这之所以成为可能，是因为在无血清的情况下，电阻增加了10倍，达到1700Ω·cm²。这些脉络丛上皮细胞将酚红、荧光素、核黄素和青霉素G从顶端转运至基底外侧。测定了米氏常数（KM值）和最大反应速度（vmax），其接近体内值。丙磺舒的竞争性抑制表明有机阴离子转运体参与其中。然而，核黄素的转运并未被完全抑制，并且对阻断Cl⁻/HCO₃⁻交换体的芪衍生物SITS没有定量反应。我们推测存在一种额外的核黄素转运系统。在体外，抗坏血酸和肌醇从基底外侧转运至顶端，这与体内从血液到脑脊液的转运非常相似。同样，体外实验的KM值接近体内值。因此，建立的上皮细胞培养模型紧密模拟了血脑屏障，可能是进一步阐明进出大脑转运的有用工具。
