| Abstract: | Suspension cultures of BHK cells grow in MEM supplemented with 10% fetal calf serum at about 50% the rate of corresponding monolayer cultures. If the serum supplement is reduced to 2% no increase in cell number is observed. When 10% serum is used small spheroids comprising 3–4 cells form within a 24 h period, but in 2 % serum the cells remain single over the same period. The addition of cycloheximide to contact-inhibited monolayer cultures induces high levels of ConA agglutinability within 6 h, yet growing non-confluent cells are rendered only about half as agglutinable by the same treatment. Cycloheximide treatment of suspension cultures causes growing cells to become agglutinable, but non-growing cells, which do not form spheroids, remain non-agglutinable even after 24 h of treatment. This suggests that the pronounced effect of cycloheximide on the agglutinability of contact-inhibited cells in monolayer culture reflects their confluence rather than suspended growth, and that the turnover rate of surface molecules determining the agglutinability state of cells is enhanced as cell-to-cell contact increases. |
