Biphasic rate of synthesis of glycoconjugates, phospholipids and DNA in concanavalin A‐stimulated mouse thymocytes. Involvement of cortisone‐sensitive and ‐resistant subpopulations

Abstract

The time course of the rate of labeling of membrane components (phospholipids, glycolipids and glycoproteins) and DNA was followed in concanavalin A-stimulated CBA/J mouse thymocyte cultures. Two peaks of stimulated biosynthetic activity were noted, the first at the beginning of the cultivation and the second about 25 h later. Both early and late peaks of biosynthesis of membrane components were accompanied by blast transformation and were unimpeded by suppression of DNA synthesis by hydroxyurea. Cortisone-sensitive and cortisone-resistant thymocytes were prepared by selective agglutination of the cortisone-sensitive cells with peanut agglutinin (Reisner et al. Cell. Immunol. 1976. 25: 129) or cortisone treatment of the animals. Cortisone-sensitive cells responded early, while the cortisone-resistant population gave only the late response. The autoradiographic patterns from sodium dodeeyl sulfate polyacrylamide gels of [³H]fucose or [³H]galactose-labeled glycoproteins from early and late labeling cells, and cortisone-resistant cells, were compared. Late-labeling and cortisone-resistant cells gave indistinguishable patterns, but differed significantly in their patterns from early-labeling cells. It is concluded that the two peaks of biosynthetic activity during the course of concanavalin A stimulation of thymocytes are caused by two different cell populations which require different times for maximal response and react independently of one another.