Rozanov A J, Jakubyk E
Ukr Biokhim Zh. 1977 Sep-Oct;49(5):54-9.
Isolated leukocytes with the presence of 14C-nicotinate in physiological concentrations (1 mg%) uptake it intensely from the dilute plasm for 6h. Dynamics of the uptake is characterized by two maxima (30-50 min and 3-5 h) which might reflect metabolic transformation of vitamin PP in leukocytes. Isolated erythrocytes and blood plasma proteins under these conditions accumulate the labelled vitamin in the largest amounts for first minutes of incubation without subsequent changes, accumulation of the labelled nicotinate by erythrocytes is 20 times as low as that by leukocytes. Kinetics of 14C-nicotinate uptake in increasing concentrations (from 4.0 up to 50.0 mM) by isolated leukocytes indicates to a system of this vitamin intake through the plasmatic membrane ensuring its intensive transport into cells with the present of 3.0-6.5 mM of nicotinic acid and a step inhibition of the label accumulation at higher concentrations which reflects decompensation of the vitamin-barrier function of the leukocytes plasma membranes with a rise in the nicotinate concentration in the medium from 6.5 to 16.3 mM the label accumulation is inhibited not only by leukocytes but also by erythrocytes. However the blood plasma proteins still bind 14C-nicotinate when it is present in the medium in linearly increasing high concentrations (16.0 = 50 mM).
分离出的白细胞在生理浓度（1毫克%）的14C - 烟酸盐存在下，会在6小时内从稀释血浆中强烈摄取该物质。摄取动态的特征是有两个峰值（30 - 50分钟和3 - 5小时），这可能反映了白细胞中维生素PP的代谢转化。在这些条件下，分离出的红细胞和血浆蛋白在孵育的最初几分钟内积累标记维生素的量最大，且随后没有变化，红细胞积累标记烟酸盐的量比白细胞低20倍。分离出的白细胞对浓度不断增加（从4.0到50.0毫摩尔）的14C - 烟酸盐的摄取动力学表明，存在一个通过质膜摄取这种维生素的系统，该系统确保其在存在3.0 - 6.5毫摩尔烟酸的情况下大量转运到细胞中，并且在较高浓度下标记积累会受到逐步抑制，这反映了随着培养基中烟酸盐浓度从6.5毫摩尔上升到16.3毫摩尔，白细胞质膜的维生素屏障功能失代偿，此时不仅白细胞的标记积累受到抑制，红细胞的标记积累也受到抑制。然而，当培养基中14C - 烟酸盐以线性增加的高浓度（16.0 = 50毫摩尔）存在时，血浆蛋白仍会结合它。
