Increased adhesiveness at sites of high acetylcholine receptor density on embryonic amphibian muscle cells cultured without nerve.

In culture, myotomal muscle cells from Xenopus laevis embryos develop discrete patches of high acetylcholine receptor (AChR) density. To examine the relative adhesiveness of these sites, muscle cells having AChR patches on their lower surface (apposed to the culture dish) were identified and were then treated with dibucaine or potassium-Ringer in order to cause the cells to round up. More than 90% of these cells remained attached at an AChR patch after rounding up, and this was the case even when the cells had a single patch on their lower surface. When the cells were torn away from the culture dish by mechanical agitation, small cellular fragments still remained firmly attached to the dish and many of these fragments contained an AChR patch. It is concluded that AChR patches on the lower surface of the cell are often located at sites of increased adhesiveness to the culture dish. The findings are discussed in terms of the formation and maintenance of AChR patches.