Hossner K L, Billiar R B
Endocrinology. 1981 May;108(5):1780-6. doi: 10.1210/endo-108-5-1780.
Plasma clearance of intact and desialylated rat and human transcortin after iv injection into rats and hamsters has been investigated. Intact rat transcortin was shown to have an approximately 5-fold longer half-life in the rat circulation than human transcortin. Removal of sialic acid residues resulted in a reduction of the half-life of rat transcortin from 4 h to 90 sec. This rapid clearance could be blocked by simultaneous injection of asialofetuin, but the clearance of intact rat transcortin was unaffected by asialofetuin. Five rat organs (pancreas, uterus, kidney, liver, and psoas muscle) were sampled at 30 and 60 min after injection of iodinated rat or human transcortin and examined for their intact transcortin levels relative to those of plasma and [14C]sucrose distribution volumes. With the exception of the liver, the organs had lower tissue:plasma ratios of [125I]iodo-transcortin than did [14C]sucrose. Liver was found to accumulate 3--8 times more human [125I]iodo-transcortin than rat [125I]iodo-transcortin, suggesting that this organ plays a greater role in the degradation and plasma clearance of human transcortin. When injected into hamsters, rat and human transcortin both had relatively long half-lives (5.8 and 6.8 h, respectively), which were dramatically shortened when sialic acid was removed. Our results suggest that the differences observed in the half-lives of these two species of transcortin in the rat are most likely due to differences in the metabolism of these two transcortins by the endogenous neuraminidase(s).
已对完整的和去唾液酸的大鼠及人皮质素结合球蛋白经静脉注射到大鼠和仓鼠体内后的血浆清除情况进行了研究。结果显示，完整的大鼠皮质素结合球蛋白在大鼠循环中的半衰期比人皮质素结合球蛋白长约5倍。去除唾液酸残基导致大鼠皮质素结合球蛋白的半衰期从4小时缩短至90秒。这种快速清除可通过同时注射去唾液酸胎球蛋白来阻断，但完整的大鼠皮质素结合球蛋白的清除不受去唾液酸胎球蛋白的影响。在注射碘化大鼠或人皮质素结合球蛋白后30分钟和60分钟采集大鼠的五个器官（胰腺、子宫、肾脏、肝脏和腰大肌），并检测其相对于血浆中完整皮质素结合球蛋白水平以及[14C]蔗糖分布容积。除肝脏外，这些器官中[125I]碘代皮质素结合球蛋白的组织与血浆比值低于[14C]蔗糖。发现肝脏积累的人[125I]碘代皮质素结合球蛋白比大鼠[125I]碘代皮质素结合球蛋白多3至8倍，这表明该器官在人皮质素结合球蛋白的降解和血浆清除中起更大作用。当注射到仓鼠体内时，大鼠和人皮质素结合球蛋白的半衰期都相对较长（分别为5.8小时和6.8小时），去除唾液酸后半衰期显著缩短。我们的结果表明，在大鼠体内观察到的这两种皮质素结合球蛋白半衰期的差异很可能是由于内源性神经氨酸酶对这两种皮质素结合球蛋白代谢的差异所致。
