Inaccessibility of certain Ricinus lectin binding sites due to the increase in hyaluronic acid during chick embryo development.

Chick embryo fibroblasts constitute a useful model for investigating cell surface differentiation using Ricinus lectin as a marker. Fibroblasts from 8-day chick embryos had two classes of Ricinus lectin binding sites, whereas those from 16-day embryos displayed only one class. Hyaluronidase treatment of fibroblasts from 8-day embryos had no effect on their capacity to bind Ricinus lectin; however after this treatment, 16-day cells resembled 8-day cells since the former also exhibited two classes of lectin-binding sites. Treatment with hyaluronidase released 2-5 times more hyaluronic acid from the older cells than from the younger cells. The same hyaluronidase treatment did not change the number of 8-day cells detached by trypsin from the substrate, but increased the number of detached 16-day cells. These observations suggest (i) that the greater adhesiveness to the substrate of the 16-day cells might be due to the presence on the cell surface of a larger amount of glycosaminoglycans at 16 days than at 8 days, and (ii) that the increased accumulation of hyaluronic acid on the cell surface might be involved in an alteration in the cell membrane during differentiation.