Surface labelling of senescent chick fibroblasts by lactoperoxidase-catalysed iodination

Cell surface of chick fibroblasts were labelled by a short treatment with 125I in presence of lactoperoxidase. A glycoprotein (220,000 molec. wt) was iodinated and was present in a more exposed position or in greater amounts at the surface of old phase III cells compared to young phase II cells. The findings extend our previous observations on cell surface modifications in in vitro senescing fibroblasts.