The influence of trace elements on calcium phosphate formation by matrix vesicles.
The effects of two inhibitors, fluoride (F-) and zinc (Zn2+), were studied on the formation of mineral by matrix vesicles (MV) in an in vitro system. Kinetically, mineral formation by MV incubated in a synthetic cartilage lymph (SCL) is characterized by three phases: a lag period, a period of rapid uptake, and finally a period of slow uptake. Zn2+ at > or = 5 microM completely inhibited MV mineralization; at < or = 1 microM, it had little effect on rate of ion uptake, but delayed conversion of an OCP-like intermediate into hydroxyapatite (OHAp). F- at > or = 10 microM reduced the rate of rapid uptake by MV and caused the OCP-like precursor to convert to OHAp. When synthetic OCP was seeded into SCL, mineralization ensued and OHAp became the dominant phase. With Zn2+ present, OCP-like features persisted longer; with F-, the OCP-like features were lost more rapidly. When ACP was seeded into SCL, OHAp formed; Zn2+ at < or = 1 microM caused OCP-like mineral to form. Our findings indicate that Zn2+ stabilizes a noncrystalline precursor in MV regulating the length of the lag period; Zn2+ also favors the formation of an OCP-like intermediate whose growth accounts for the rapid uptake phase. This OCP-like phase appears to nucleate formation of OHAp by MV.
Sauer
G R
GR
Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA.
Wu
L N
LN
Iijima
M
M
Wuthier
R E
RE
D000818:Animals; D002113:Calcification, Physiologic; D002130:Calcium Phosphates / Q000378:metabolism*; D002645:Chickens; D005109:Extracellular Matrix / Q000378:metabolism* / Q000648:ultrastructure; D005459:Fluorides / Q000494:pharmacology*; D006132:Growth Plate / Q000378:metabolism* / Q000648:ultrastructure; D066298:In Vitro Techniques; D017550:Spectroscopy, Fourier Transform Infrared; D015032:Zinc / Q000494:pharmacology*
D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485830:tetracalcium phosphate; C485838:calcium phosphate, monobasic, anhydrous; C020243:calcium phosphate; D015032:Zinc; C485829:calcium phosphate, dibasic, anhydrous; D005459:Fluorides