Long G J, Pounds J G, Rosen J F
Department of Pediatrics, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York 10467.
Calcif Tissue Int. 1992 May;50(5):451-8. doi: 10.1007/BF00296777.
The skeleton is the major reservoir of lead and calcium in humans, and plays an important role in systemic calcium regulation. Lead perturbs normal calcium transport and second messenger function, directly or indirectly, in virtually all cells studies so far. Therefore, we and others have postulated that an early and discrete toxic effect of lead is perturbation of one or more loci within the calcium messenger system. To understand further the role of lead on calcium homeostasis in bone, we undertook this study to characterize calcium homeostasis and the effect of lead on calcium homeostasis in rat osteosarcoma (ROS 17/2.8) cells, which exhibit the osteoblast phenotype. ROS cells were incubated in medium containing 45Ca for 20 hours. Monitoring the efflux of 45Ca from the cultures for 210 minutes allowed for the determination of kinetic parameters defining steady state calcium homeostasis. Three distinct intracellular kinetic calcium pools characterized 45Ca homeostasis. Treatment with either 400 ng parathyroid hormone (PTH)/ml culture medium for 1 hour or 25 microM lead for 20 hours increased total cell calcium. Treatment with PTH caused a larger increase of cell calcium in lead-intoxicated cells than either lead intoxication or PTH treatment alone. This increase suggests that lead may perturb normal calcium-mediated PTH responsiveness of the osteoblast. These experiments further establish a kinetic model for the study of calcium homeostasis in osteoblastic bone cells. The studies also advance the hypothesis that lead-induced perturbations of calcium-mediated processes represent an early effect of lead toxicity at the cellular level.
骨骼是人体中铅和钙的主要储存库，在全身钙调节中发挥着重要作用。迄今为止，在几乎所有研究的细胞中，铅直接或间接干扰正常的钙转运和第二信使功能。因此，我们和其他人推测，铅的早期离散毒性作用是干扰钙信使系统中的一个或多个位点。为了进一步了解铅在骨钙稳态中的作用，我们进行了这项研究，以表征大鼠骨肉瘤（ROS 17/2.8）细胞中的钙稳态以及铅对钙稳态的影响，这些细胞表现出成骨细胞表型。将ROS细胞在含有45Ca的培养基中孵育20小时。监测培养物中45Ca的流出210分钟，以便确定定义稳态钙稳态的动力学参数。三个不同的细胞内动力学钙池表征了45Ca稳态。用400 ng甲状旁腺激素（PTH）/ml培养基处理1小时或用25 microM铅处理20小时可增加细胞总钙含量。与单独的铅中毒或PTH处理相比，用PTH处理导致铅中毒细胞中的细胞钙增加更大。这种增加表明铅可能会干扰成骨细胞正常的钙介导的PTH反应性。这些实验进一步建立了一个动力学模型，用于研究成骨细胞性骨细胞中的钙稳态。这些研究还推进了这样一种假设，即铅诱导的钙介导过程的扰动代表了铅在细胞水平上毒性的早期效应。
