1,25-Dihydroxyvitamin D3 enhances degranulation of mast cells1This work was presented in part at the annual meeting of the American Society for Bone and Mineral Research, 1996 (J. Bone Miner. Res. 11 (Suppl 1) S429) and at the 10th Workshop on Vitamin D, 1997.1

1998 ◽  
Vol 142 (1-2) ◽  
pp. 49-55 ◽  
Author(s):  
M Shalita-Chesner ◽  
R Koren ◽  
Y.A Mekori ◽  
D Baram ◽  
C Rotem ◽  
...  
Keyword(s):  
Vitamin D ◽  
Annual Meeting ◽  
Mineral Research ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
American Society

Rat renal 25-hydroxyvitamin D3 1- and 24-hydroxylases: their in vivo regulation

1984 ◽  
Vol 246 (2) ◽  
pp. E168-E173 ◽  
Author(s):  
Y. Tanaka ◽  
H. F. DeLuca
Keyword(s):  
Vitamin D ◽  
Inorganic Phosphorus ◽  
Hydroxylase Activity ◽  
Deficient Diet ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Dietary Phosphorus ◽  
Low Calcium

The effects of thyroparathyroidectomy, parathyroid hormone, 1,25-dihydroxyvitamin D3, dietary calcium, dietary phosphorus, age, and sex on the renal 25-hydroxyvitamin D3 1- and 24-hydroxylases measured in vitro in rats have been studied. Thyroparathyroidectomy of vitamin D-deficient rats abolishes 25-hydroxyvitamin D3 1-hydroxylase activity, and administration of bovine parathyroid extract to the thyroparathyroidectomized rat restores diminished 1-hydroxylase activity. Both suppression and restoration of the enzyme activities require many hours (18-24 h) independent of rapid changes in serum calcium and inorganic phosphorus levels in response to these manipulations. Administration of 1,25-dihydroxyvitamin D3 to vitamin D-deficient rats suppresses 25-hydroxyvitamin D3 1-hydroxylase activity and stimulates 25-hydroxyvitamin D3 24-hydroxylase activity within 48 h. Rats maintained on a low-calcium or a low-phosphorus diet with a daily supplement of 20 IU vitamin D3 show high 25-hydroxyvitamin D3 1-hydroxylase activity and low 24-hydroxylase activity as compared with rats similarly treated but fed a diet containing adequate calcium or adequate phosphorus. When vitamin D-sufficient rats having suppressed renal 25-hydroxyvitamin D3 1-hydroxylase activity are placed on a low-calcium vitamin D-deficient diet for 7 days, the 1-hydroxylase activity is greatly stimulated in 6-wk-old rats but much less so in rats with advancing age.

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