Primary hyperparathyroidism is a relatively common endocrine dysfunction with an incidence of 40-45 cases per 100,000 population. Secondary hyperparathyroidism is a manifestation of renal failure. There are over 100,000 patients on dialysis in the United States. Thus, disorders of parathyroid function impose a significant burden on health care management and loss from the labor force each year. The control of parathyroid hormone secretion is almost unique in that calcium ultimately inhibits secretion whereas in most other systems calcium stimulates secretion. This investigation focuses on molecular mechanisms that are involved in the control of calcium-mediated PTH secretion. The role of GTP-binding signal transducing proteins and protein kinase C in normal parathyroid secretion will be studied. Synthetic oligonucleotide probes will be used to select for DNA sequences in a normal bovine parathyroid expression library constructed in phage lambda gtl0. The DNA corresponding to the signal transduction proteins will be subcloned and sequenced by the dideoxy chain-termination method to deduce the types of GTP-binding proteins expressed in the parathyroid cell. This will establish whether the parathyroid cell contains signal transduction proteins common to other secretory tissues, or if there is a unique transducing protein to the parathyroid which can account for the reverse calcium sensitivity of hormone secretion. Based upon the derived amino acid sequences, peptides of specific sequence will be synthesized. These peptides will be used to generate polyclonal antisera specific to the individual signal transduction proteins in order to quantitate these proteins in parathyroid cells. The transducing proteins which serve as substrates for pertussis toxin and cholera toxin, and a toxin-insensitive protein linked to phospholipase C will be characterized. The effect of pertussis toxin and cholera toxin on calcium, magnesium and strontium-induced suppression of PTH secretion and changes in cytosolic calcium will be evaluated. The role of protein kinase C in parathyroid secretion will be evaluated by monitoring enzyme activity, and through the use of anti-peptide antisera specific for the three isoforms of protein kinase C. Sphingoid base metabolism as a function of extracellular calcium, magnesium and strontium will be evaluated for the production of protein kinase C inhibitors. These studies utilizing the parathyroid expression library, DNA sequencing and antipeptide antibodies will form a basis for the future examination of normal and abnormal parathyroid function.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK030178-09A1
Application #
3229318
Study Section
General Medicine B Study Section (GMB)
Project Start
1990-07-01
Project End
1993-06-30
Budget Start
1990-07-01
Budget End
1991-06-30
Support Year
9
Fiscal Year
1990
Total Cost
Indirect Cost
Name
Washington University
Department
Type
Schools of Medicine
DUNS #
062761671
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Slatopolsky, Eduardo (2011) The intact nephron hypothesis: the concept and its implications for phosphate management in CKD-related mineral and bone disorder. Kidney Int Suppl :S3-8
Takahashi, Fumiaki; Denda, Masashi; Finch, Jane L et al. (2002) Hyperplasia of the parathyroid gland without secondary hyperparathyroidism. Kidney Int 61:1332-8
Dusso, A S; Pavlopoulos, T; Naumovich, L et al. (2001) p21(WAF1) and transforming growth factor-alpha mediate dietary phosphate regulation of parathyroid cell growth. Kidney Int 59:855-65
Huang, Z; Cheng, S L; Slatopolsky, E (2001) Sustained activation of the extracellular signal-regulated kinase pathway is required for extracellular calcium stimulation of human osteoblast proliferation. J Biol Chem 276:21351-8
Brown, A J; Finch, J; Takahashi, F et al. (2000) Calcemic activity of 19-Nor-1,25(OH)(2)D(2) decreases with duration of treatment. J Am Soc Nephrol 11:2088-94
Holliday, L S; Gluck, S L; Slatopolsky, E et al. (2000) 1,25-Dihydroxy-19-nor-vitamin D(2), a vitamin D analog with reduced bone resorbing activity in vitro. J Am Soc Nephrol 11:1857-64
Slatopolsky, E; Brown, A; Dusso, A (1999) Pathogenesis of secondary hyperparathyroidism. Kidney Int Suppl 73:S14-9
Brown, A J; Ritter, C S; Finch, J L et al. (1999) Decreased calcium-sensing receptor expression in hyperplastic parathyroid glands of uremic rats: role of dietary phosphate. Kidney Int 55:1284-92
Slatopolsky, E; Dusso, A; Brown, A J (1999) The role of phosphorus in the development of secondary hyperparathyroidism and parathyroid cell proliferation in chronic renal failure. Am J Med Sci 317:370-6
Huang, Z; Ritter, C; Brown, A et al. (1999) Cloning and localization of Rab3 isoforms in bovine, rat, and human parathyroid glands. Biochem Biophys Res Commun 255:645-51

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