Kirchgessner M, Reuber S, Kreuzer M
Institut für Ernährungsphysiologie, Technische Universität München-Weihenstephan, Freising, Germany.
Biol Trace Elem Res. 1994 Apr-May;41(1-2):175-89. doi: 10.1007/BF02917227.
At the end of a 49-d experiment with 32 growing male rats, a period of 8 d was used to determine endogenous excretion and true absorption as well as apparent absorption and retention of cobalt with the aid of the isotope dilution technique. For this purpose, a single im dose of 58Co was applied at d 35 of the experiment. After that, urine and feces were collected separately from d 8 to 15 after injection of the isotope. The specific cobalt activity of the liver was used as an endogenous reference source. The basal diet provided 5.9 ppb cobalt, the different treatment groups were obtained by supplementing the diet with 0, 10, 50, 250, or 1250 ppb cobalt. The different diets were offered from the beginning of the experiment. In the balance period, apparent and true absorption as well as fecal excretion behaved similar to cobalt intake, whereas urinary excretion increased more rapidly with increasing cobalt supply. Endogenous fecal excretion accounted for 3.5 ng Co/d in the groups fed the diets without and with 10 ppb cobalt. An increase was not observed until supplementing the diet with 50 ppb cobalt. This increase between 250 and 1250 ppb cobalt was higher than the corresponding increase in the dietary cobalt supply. This indicates that endogenous fecal excretion might be more important for homeostatic regulation at a higher dietary cobalt concentration. Endogenous renal excretion as calculated from the results of the isotope dilution technique showed a similar kind of response to increasing cobalt supply as endogenous fecal loss. Nevertheless, the elimination of excessive cobalt mainly took place by adjusting urinary excretion, whereas the variations in true absorption and endogenous fecal excretion had no quantitative importance. Apparent and true absorption were on average 28.0 and 29.8%, respectively, of the cobalt intake. In the case of retention, a marked decline was observed from 19% in the depletion group to 3% with 1250 ppb cobalt, again demonstrating the importance of urinary excretion for controlling the cobalt content of the organism.
在对32只生长中的雄性大鼠进行的为期49天的实验结束时，利用同位素稀释技术，用8天时间来测定钴的内源性排泄、真吸收以及表观吸收和潴留情况。为此，在实验的第35天单次腹腔注射58Co。之后，在注射同位素后的第8天至第15天分别收集尿液和粪便。肝脏的比钴活度用作内源性参考源。基础日粮提供5.9 ppb钴，通过在日粮中分别添加0、10、50、250或1250 ppb钴获得不同的处理组。从实验开始就提供不同的日粮。在平衡期，表观吸收和真吸收以及粪便排泄与钴摄入量的表现相似，而随着钴供应量的增加，尿排泄增加得更快。在饲喂不含钴和含10 ppb钴日粮的组中，内源性粪便排泄量为3.5 ng Co/天。直到日粮中添加50 ppb钴时才观察到增加。在250至1250 ppb钴之间的这种增加高于日粮钴供应量的相应增加。这表明在较高日粮钴浓度下，内源性粪便排泄可能对稳态调节更为重要。根据同位素稀释技术结果计算的内源性肾脏排泄对钴供应量增加的反应与内源性粪便损失相似。然而，过量钴的消除主要通过调节尿排泄进行，而真吸收和内源性粪便排泄的变化没有定量意义。表观吸收和真吸收分别平均为钴摄入量的28.0%和29.8%。在潴留方面，观察到明显下降，从耗竭组的19%降至含1250 ppb钴时的3%，再次证明尿排泄对控制机体钴含量的重要性。
