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Cell Membrane Sialoglycopeptides of Corticoid-sensitive and -resistant Lymphosarcoma P1798¹

Research Institute, Hospital for Joint Diseases, Mount Sinai School of Medicine, New York, New York 10035

Cells of corticoid-sensitive (CS) and corticoid-resistant (CR) lymphosarcoma P1798 were labeled in vivo with either [¹⁴C]- or [³H]fucose before and after treatment with 9--fluoroprednisolone (9-FP). Labeled glycopeptides, derived from isolated, Pronase-digested cell membranes of both tumors were separated by gel filtration on Bio-Gel P-10 by a double-label technique. Elution profiles of CS and CR fractions showed significant differences in early eluting material. Desialylation of glycopeptides by neuraminidase lowered the molecular weight of both CS and CR fractions, and altered ³H:¹⁴C ratios indicated that CS and CR sialoglycopeptides are different. 9-FP treatment for 7 hr increased the density of isolated P1798-CS and -CR cell membranes. All CS and CR glycopeptides from treated tumors eluted faster than did those of untreated preparations. Both CS and CR sialoglycopeptides were altered, although differences in CS and CR profiles persisted. Histochemical investigations indicated that negative charge, present on surfaces of untreated CS cells, is lost between 6 and 8 hr after exposure in vivo to 9-FP. CR cells had no or few anionic sites on their surfaces before and after steroid administration. We demonstrated that glycopeptides of both CS and CR tumors contain sialic acid, although only CS cells carry a surface-exposed negative charge that is lost after 9-FP treatment. Glucocorticoids after both P1798-CS and -CR sialoglycopeptides, but the consistent differences between their chromatographic patterns suggest that steroid-induced changes in cell membranes of the two tumors are not identical. Cell death or survival of glucocorticoid-treated P1798 cells may, therefore, be influenced by specific structural characteristics involving cell surface sialoglycoproteins.

¹ This investigation was supported by USPHS Research Grant CA-14194 and CA-10064 from the National Cancer Institute.

² The studies reported in this paper are presented in partial fulfillment of the requirements of the Ph.D. degree at the City University of New York.

³ To whom requests for reprints should be addressed.

Received 5/22/75. Accepted 9/16/75.