Coordinate inhibition of alkaline phosphatase and type X collagen syntheses by 1,25-dihydroxyvitamin D3 in primary cultured hypertrophic chondrocytes.
The effects of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) (2.3 x 10(-12) - 1.4 x 10(-6) [M]) on alkaline phosphatase, collagen, and cell proliferation were examined in primary cultured hypertrophic chondrocytes prepared from the distal epiphyseal growth plate of the tibias of 12-day chick embryos. 1,25(OH)2D3 showed time- and dose-dependent inhibitory effects on the alkaline phosphatase and collagen levels. The inhibition of alkaline phosphatase activity became detectable at 2 x 10(-11) [M] and reached 10% of control at 10(-7) [M]. The concentration of 1,25(OH)2D3 giving a 50% inhibition of the enzyme level was approximately 3 x 10(-10) [M]. Of the two extracellular collagen pools, a cell-associated matrix pool showed a more dramatic decrease (to 10% of control) than a culture medium pool (to 50% of control) at increased 1,25(OH)2D3 concentrations. The degree of inhibition was different for each type of chondrocyte-specific collagen (types II, IX, X, and XI). Types II and IX were inhibited in a parallel manner to only 60-80% of control. On the other hand, types X and XI were more greatly reduced up to 10% of control, and their dose-dependent inhibitory curves were similar to that of alkaline phosphatase. On cell proliferation, 1,25(OH)2D3 had a biphasic effect: stimulation at 10(-10)-10(-8) [M] and inhibition at higher levels. The results revealed the significant involvement of 1,25(OH)2D3 in the metabolism of two probable calcification-related products, alkaline phosphatase and type X collagen.
Inao
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Department of Biochemistry, University of Illinois, Urbana.
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D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors*; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002356:Cartilage / Q000378:metabolism* / Q000473:pathology*; D002478:Cells, Cultured; D002642:Chick Embryo; D003094:Collagen / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D006984:Hypertrophy; D013997:Time Factors
D003094:Collagen; D000469:Alkaline Phosphatase; D002117:Calcitriol