Surface Labelling of Senescent Chick Fibroblasts by Lactoperoxidase-Catalysed Iodination

Abstract

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.

Organ‐Dependent Expression of Differentiated States in Fibroblasts Cultured in Vitro

“…It has been known that undifferentiated cells are small in size and very proliferative, but differentiated cells are large in size and arrest their cell cycle (4, 35). Changes in the activity of synthesis and secretion of extracellular components, collagen and fibronectin, with age are controversial among authors (11,19,25,27,37). The relationship between the extent of differentiation and the activity of synthesis of extracellular substances has not been examined yet in fibroblasts.…”

Identification of cell surface polypeptides encoded by human chromosomes 2 and 5 in human-mouse somatic cell hybrids

“…Seventy-two hours later, the medium was as pirated, and the cells were washed three times with phosphatebuffered saline (PBS) at 37 °C; each wash was left on the cells for 5 min. After the third wash, the cells were incubated with 1 ml of 5 mM glucose in PBS, 0.3 ml lactoperoxidase (0.2 mg/ml in PBS, Sigma), 0.3 ml glucose oxidase (approximately 2800 units of activity/ml, Sigma), and 0.5 mCi carrier-free N al25I (100 mCi/ml, New England Nuclear) per flask for 1 h at room temperature with occasional rocking as described by Courtois and Hughes (1976). At the end of the labeling period, the reaction mixture was decanted, and the cells were rinsed four times with 50 mM potassium iodide in PBS and scraped off the flask with a rubber policeman into 2 mM phenylmethylsulfonyl flouridc in PBS.…”