Bone is the major reservoir of body lead (Pb) stores in humans; and it is now recognized, based upon in vivo and in vitro data, that one skeletal subcompartment of bone Pb is readily exchangeable and modulated in a manner similar to that of calcium (Ca). Moreover, the skeleton is the site of Pb chelation by CaNa2EDTA; and recent clinical observations in children indicate that the skeleton is a target tissue for Pb's toxic effects. Within this context, our laboratory's primary efforts are directed at testing the postulate that pertubations in cellular Ca homeostasis, produced by Pb at relatively low concentrations, is an early and discrete expression of Pb toxicity at the cellular level. Such pertubations are likely to be far reaching and may place the regulation of multiple cellular processes out of the physiological range of normal control through changes in intracellular ionic Ca concentration. Experiments carried out by us in primary monolayer cultures of separated osteoclastic (OC) and osteoblastic (OB) bone cells, during the previous grant period, further confirm and extend this postulate to the point where it can now be verified directly.
The specific aims of the proposal are to: 1) characterize the steady state kinetic distribution and modulation of Pb and Ca in OB by desaturation techniques; 2) measure directly by 19F NMR the concentration of cytosolic free Ca and Pb concurrently in OC and OB with and without Pb (and calciotropic hormones) in the medium; 3) determine the specific mechanisms of Pb-Ca interactions at the level of membrane transport, where Pb effects on Ca transport in isolated membranes will be examined in resting and hormonally stimulated OC and OB; 4) define the effects of Pb on Ca-mediated cell functions and the generation and degradation of cAMP; 5) characterize further Pb influences on the integrated functions of OC and OB separately and together in co-culture experiments. Taken together, the proposed quantitative, mechanistic and functional studies in OB and OC have the real potential to define, for the first time, the molecular basis of early Pb toxicity at the cellular level.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Method to Extend Research in Time (MERIT) Award (R37)
Project #
5R37ES001060-20
Application #
2153029
Study Section
Special Emphasis Panel (NSS)
Project Start
1977-05-01
Project End
1996-11-30
Budget Start
1994-12-01
Budget End
1995-11-30
Support Year
20
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Montefiore Medical Center (Bronx, NY)
Department
Type
DUNS #
City
New York
State
NY
Country
United States
Zip Code
10467
Finkelstein, Y; Markowitz, M E; Rosen, J F (1998) Low-level lead-induced neurotoxicity in children: an update on central nervous system effects. Brain Res Brain Res Rev 27:168-76
Long, G J; Rosen, J F; Schanne, F A (1994) Lead activation of protein kinase C from rat brain. Determination of free calcium, lead, and zinc by 19F NMR. J Biol Chem 269:834-7
Long, G J; Rosen, J F (1994) Lead perturbs 1,25 dihydroxyvitamin D3 modulation of intracellular calcium metabolism in clonal rat osteoblastic (ROS 17/2.8) cells. Life Sci 54:1395-402
Dowd, T L; Rosen, J F; Gundberg, C M et al. (1994) The displacement of calcium from osteocalcin at submicromolar concentrations of free lead. Biochim Biophys Acta 1226:131-7
Rosen, J F; Crocetti, A F; Balbi, K et al. (1993) Bone lead content assessed by L-line x-ray fluorescence in lead-exposed and non-lead-exposed suburban populations in the United States. Proc Natl Acad Sci U S A 90:2789-92
Schanne, F A; Gupta, R K; Rosen, J F (1992) Lead inhibits 1,25-dihydroxyvitamin D-3 regulation of calcium metabolism in osteoblastic osteosarcoma cells (ROS 17/2.8). Biochim Biophys Acta 1180:187-94
Long, G J; Pounds, J G; Rosen, J F (1992) Lead intoxication alters basal and parathyroid hormone-regulated cellular calcium homeostasis in rat osteosarcoma (ROS 17/2.8) cells. Calcif Tissue Int 50:451-8
Rosen, J F (1992) Health effects of lead at low exposure levels. Expert consensus and rationale for lowering the definition of childhood lead poisoning. Am J Dis Child 146:1278-81
Long, G J; Rosen, J F (1992) Lead perturbs epidermal growth factor (EGF) modulation of intracellular calcium metabolism and collagen synthesis in clonal rat osteoblastic (ROS 17/2.8) cells. Toxicol Appl Pharmacol 114:63-70
Long, G J; Rosen, J F; Pounds, J G (1990) Lead impairs the production of osteocalcin by rat osteosarcoma (ROS 17/2.8) cells. Toxicol Appl Pharmacol 106:270-7

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