CYCLIC AMP MEDIATES THE CONCANAVALIN A AGGLUTINABILITY OF MOUSE FIBROBLASTS

We have devised a quantitative way to measure the agglutination of cells which utilizes the size discrimination feature of an automatic particle counter. With this method we have studied the agglutinability by concanavalin A of 3T3 cells, a mutant of 3T3 cells (3T3cAMP^tcs) in which cyclic AMP levels fall when the cells are subjected to temperature change or fresh serum, and L929 cells. We find with 3T3cAMP^tcs cells that low levels of cyclic AMP correlate with increased agglutinability and that high levels of cyclic AMP correlate with decreased agglutinability. Prior treatment of these cells with a cyclic AMP phosphodiesterase inhibitor or Bt₂cAMP blocks the increase in agglutinability induced by temperature change. When 3T3 cells are treated with fresh serum, their agglutinability also increases although to a much smaller extent than with 3T3cAMP^tcs cells. Cells change their agglutinability very rapidly. Treatment of L929 cells for 15 min with 1-methyl-3-isobutyl xanthine at 1 mM decreases their agglutinability to the level of normal 3T3 cells. We conclude that in normal and transformed cells the level of cyclic AMP regulates agglutinability.