STEREOSPECIFIC INHIBITION OF ALKALINE-PHOSPHATASE BY L-TETRAMISOLE PREVENTS INVITRO CARTILAGE CALCIFICATION

  • 1 January 1980
    • journal article
    • research article
    • Vol. 43  (6) , 489-494
Abstract
To clarify the role of alkaline phosphatase (ALP) and ATPase in skeletal mineralization, the effect of the anthelmintic drug, l-tetramisole (levamisole), a stereospecific inhibitor of ALP activity, and its inactive isomer, d-tetramisole (dexamisole) was studied on in vitro calcification of rachitic rat cartilage. ALP activity in homogenized rachitic rat proximal tibiae was inhibited by l-tetramisole in a dose-dependent manner. Histochemical and EM cytochemical analysis of intact epiphyseal plate rachitic rat cartilage showed that 5 .times. 10-2 M and greater concentrations of l-tetramisole virtually abolished ALP activity, moderately reduced ATPase activity and prevented in vitro cartilage calcification, while preserving the structural integrity of the matrix vesicles. Concentrations of d-tetramisole as high as 1 .times. 10-1 M failed to inhibit ALP activity in tibial homogenates by > 10% and did not alter histochemical staining of enzyme activity or calcification of intact cartilage slices. Heating the cartilage slices destroyed ALP activity, prevented calcification and disrupted matrix vesicle integrity. There is a close association between ALP activity and in vitro calcification of rachitic rat cartilage. In the absence of ALP activity, intact matrix vesicles do not promote calcification. Some ATPase activity of rachitic vesicles do not promote calcification. Some ATPase activity of rachitic rat cartilage may be distinct from ALP activity.