Effects of diastereoisomers of 1,25-dihydroxyvitamin D3-26,23-lactone on alkaline phosphatase and collagen synthesis in osteoblastic cells

Seiichi Ishizuka, Mamoru Kiyoki, Noriyoshi Kurihara, Yoshiyuki Hakeda, Katsumi Ikeda, Masayoshi Kumegawa, Anthony W. Norman

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

The effects of the four diastereoisomers of 1,25-dihydroxyvitamin D3-26,23-lactone (1,25-(OH)2D3-26,23-lactone) on alkaline phosphatase (AP) activity and collagen and noncollagen protein synthesis were examined in cultures of the osteoblastic clone MC3T3-E1 cell line. The four lactone diastereoisomers had little effect on the protein and DNA content of the cells. The 23(S),25(S)- and 23(R),25(R)-1,25-(OH)2D3-26,23-lactones increased AP activity in a linear dose-dependent fashion. Maximal effects were observed at 100 and 1000 pg/ml, respectively. In contrast, the naturally occurring 23(S),25(R)-, 1,25-(OH)2 D3-26,23-lactone and the 23(R),25(S)-1,25-(OH)2D3-26,23-lactone showed biphasic stimulatory effects on AP activity. At both 80 and 10000 pg/ml, they stimulated maximum increases in alkaline phosphatase activity. At 80 pg/ml the 23(S),25(R)- and 23(R),25(S)-isomers stimulated an increase in collagen synthesis, while at 10000 pg/ml these isomers and 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) did not. Moreover, these two isomers (at 10000 pg/ml) plus insulin or dexamethasone had an additive effect on AP activity, but not at 80 pg/ml. At 80 pg/ml but not at 10000 pg/ml, the 23(S),25(R)-isomer had an additive effect on AP activity with the simultaneous addition of 25-hydroxyvitamin D3. Relative to 1,25-(OH)2D3, the binding affinities of 23(S),25(S)-, 23(R),25(R)-, 23(S),25(R)- and 23(R),25(R)-1,25-(OH)2 D3-26,23-lactones were calculated to be 1 13.0, 1 131.8, 1 805.2, and 1 1083.3, respectively. No metabolites could be detected in the médium when [1-3H]23(S),25(R)-1,25-(OH)2D3-26,23-lactone (the naturally occurring diastereoisomer) was added to the cultures. However, the stimulative effects of 1,25-(OH)2D3 and the 23(S),25(R)-isomer at both concentrations were completely abolished by l-1-tosyl-amido-2-phenylethyl chloromethyl ketone. These results indicate that 1,25-(OH)32D3-lactone bas a stimulative effect on osteoblastic cell functions in vitro. The naturally occurring 23(S),25(R)-1,25-(OH)2D3-lactone acts biphasically and may act on bone metabolism in vivo, possibly through a 1,25-(OH)2D3-receptor-mediated pathway.

Original languageEnglish (US)
Pages (from-to)77-86
Number of pages10
JournalMolecular and Cellular Endocrinology
Volume55
Issue number1
DOIs
StatePublished - Jan 1988
Externally publishedYes

Keywords

  • Alkaline phosphatase
  • Osteoblast
  • Vitamin D

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Endocrinology

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