Studies on the 1α,25-Dihydroxycholecalciferol-like Activity in a Calcinogenic Plant, Cestrum diurnum, in the Chick

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Abstract
Cestrum diurnum (day-blooming jessamine) has been proposed to cause calcinosis in horses and cattle in Florida. The present studies investigated some physiological properties of the plant, using the chick as the experimental animal. The inclusion of dried leaf powder in a rechitogenic diet restored intestinal calcium-binding protein synthesis (CaBP) and increased calcium absorption in the cholecalciferol-deficient chick. The estimated level of cholecalciferol-equivalents in the dried leaf was about 30,000 to 35,000 IU/kg. Most of the activity was extractable with methanol:chloroform (2:1), indicating that the major cholecalciferol-like component in C. diurnum was different from the water soluble factor(s) in Solanum malacoxylon. The time course of effect of C. diurnum extract in rachitic chicks was similar to that of 1,25-dihydroxycholecalciferol but the former had a longer lag time. The strontium fed chick, in which the kidney 25-hydroxycholecalciferol-1α-hydroxylase is inhibited, responded to C. diurnum extract, confirming the 1α, 25-dihydroxycholecalciferol-like character of the Cestrum factor. The extract also appeared to interact with the intestinal 1α,25-dihydroxycholecalciferol cytosol receptor although this observation is preliminary. These findings indicate that the 1α,25-dihydroxycholecalciferol-like principle in C. diurnum may cause excessive calcium and phosphate absorption leading to calcinosis.