Studies on the mode of action of vitamin D XXXVII 1α-hydroxyvitamin D3: A long-acting 1,25-dihydroxyvitamin D3 analog

1983 ◽  
Vol 35 (1) ◽  
pp. 372-375 ◽  
Author(s):  
Marian R. Walters ◽  
Willi Hunziker ◽  
June E. Bishop ◽  
Anthony W. Norman
Keyword(s):  
Vitamin D ◽  
Mode Of Action ◽  
Dihydroxyvitamin D3 ◽  
1,25 Dihydroxyvitamin D3 ◽  
Long Acting

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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