Recent studies have documented that 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) exerts rapid effects on cytosolic and nuclear Ca2+ levels, pH, and phospholipid metabolism. The rapid effects on cytosolic and nuclear Ca2+ also occur in osteoblast-like cell lines with (ROS 17/2.8) and without (ROS 24/1) the classic vitamin D receptor. It is our objective to further define the interrelationships between the hormone, e.g., alterations in gene transcription and response to parathyroid hormone (PTH). The 1alpha,25-(OH)2D3 rapid effects on the mobilization of intracellular Ca2+ stores do not appear to require the classic vitamin D receptor. The hormone-induced increments in Ca2+ occur in cells without the receptor (ROS 24/1) and are inhibited by the inactive epimer 1beta,25-dihydroxyvitamin D3 (1beta,25(OH)2D3), which does not bind to the classic receptor. Intracellular Ca2+, pH, and inositol lipids, as well as 1alpha,25-(OH)2D3, appear to be involved in the regulation of cell and nuclear function. Pretreatment of osteoblast-like cells with 1alpha,25-(OH)2D3 attenuates the response of these cells to PTH. Increments in intracellular Ca2+ alter gene expression. 1alpha,25-(OH)2D3 rapidly and stereospecifically increases cytosolic and nuclear Ca2+ in hepatocytes and osteoblast-like cells. The hormone-induced changes in cell pH and phospholipid metabolism precede the increments in Ca2+ in hepatocytes. These relationships in the osteoblast-like cell lines and hepatoma cells have not been defined. Likewise, the relationship between the rapid changes in Ca2+ and altered gene expression, e.g., osteocalcin and procollagen in ROS cells and c-myc in hepatoma cells, decreased collagen synthesis, and attenuated response to PTH, are unknown. It is the purpose of this proposal to 1) examine the effects of 1alpha,25-(OH)2D3 on cytosolic Ca2+, pH, and phospholipid metabolism in clonal osteosarcoma cells with and without the classic vitamin D receptor and in a human hepatoma cell line; 2) define the effects of 1alpha,25-(OH)2D3 on Ca2+ levels, pH, and phospholipid metabolism in nuclei derived from the osteoblast-like cells and normal and transformed liver cells; 3) correlate the rapid changes in the osteoblast-like cells with altered collagen synthesis and response to PTH; and 4) determine the relationship of the rapid effects of 1alpha,25-(OH)2D3 to the hormone's effects on osteocalcin and procollagen gene expression in ROS 17/2.8 cells and c-myc expression in a human hepatoma cell line.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK039085-08
Application #
2140782
Study Section
General Medicine B Study Section (GMB)
Project Start
1987-08-01
Project End
1996-06-30
Budget Start
1995-04-01
Budget End
1996-06-30
Support Year
8
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Massachusetts Medical School Worcester
Department
Orthopedics
Type
Schools of Medicine
DUNS #
660735098
City
Worcester
State
MA
Country
United States
Zip Code
01655
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Milne, M; Quail, J M; Baran, D T (1998) Dexamethasone stimulates osteogenic differentiation in vertebral and femoral bone marrow cell cultures: comparison of IGF-I gene expression. J Cell Biochem 71:382-91
Milne, M; Kang, M I; Quail, J M et al. (1998) Thyroid hormone excess increases insulin-like growth factor I transcripts in bone marrow cell cultures: divergent effects on vertebral and femoral cell cultures. Endocrinology 139:2527-34
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Baran, D T (1994) Nongenomic actions of the steroid hormone 1 alpha,25-dihydroxyvitamin D3. J Cell Biochem 56:303-6
Baran, D T; Ray, R; Sorensen, A M et al. (1994) Binding characteristics of a membrane receptor that recognizes 1 alpha,25-dihydroxyvitamin D3 and its epimer, 1 beta,25-dihydroxyvitamin D3. J Cell Biochem 56:510-7

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