Comparison of normal and rachitic rat matrix vesicles.

Accumulated information about MVs in PO4-deficient rachitic rats shows them to be normal in most aspects. Both normal and rachitic MVs show the same ultrastructural features and selective spatial distribution in the growth plate, and both contain a nearly identical array of major proteins. Rachitic and normal MVs show the same avidity to calcify in vivo and in vitro. A slightly greater specific activity of ALP in rachitic MVs may enhance their calcifiability. We conclude that rachitic rat MVs are essentially 'normal' and can be used as an adequate model to study the mechanism of biological calcification.