Endogenous peroxidase activity in primary culture of XXXX thyroid cells. Localization and measurement.

@entity1 @entity15729 @entity1792 @entity1378 @entity273 @entity3745
Intracellular localization of and an assay method for endogenous peroxidase (PO) activity were studied using primary culture of thyroid cells obtained from @entity1 with @entity1378 . PO activity was visualized by cytochemical reaction and was located mainly in perinuclear cisternae and rough endoplasmic reticulum. With increased culture time, the number of cells showing positive PO activity and amount of the enzyme reaction product in individual cells showed a parallel decrease. For measurement of PO activity, cultured thyroid cells were frozen and thawed and then incubated with @entity1792 buffer solution containing @entity15729 (opd) and @entity273 . After incubation, the optical density (OD) of the solution colorized by endogenous peroxidase was measured at 405 nm using a microplate reader. About 1 X 10(4) cells were sufficient for assay of PO activity. Using the above method to assay PO activity and sandwich enzyme immunoassay for @entity3745 (TG), chronological changes in the PO activity and TG concentration in the culture medium were examined. Although the cells showed no decrease in number, PO activity and TG concentration decreased chronologically. When the ratio of PO activity to TG concentration was calculated, in 3 cases the ratio was almost constant, and in the remaining two, it decreased chronologically. The present biochemical method thus seems useful for determining peroxidase activity of cultured thyroid en masse.
