NEXUSES BETWEEN THE SMOOTH-MUSCLE CELLS OF THE GUINEA-PIG ILEUM

The circular musculature of the guinea-pig ileum was studied by freeze-fracture to analyze quantitatively the gap junctions (nexuses) between its smooth muscle cells. The average cell surface area and cell volume are 5074 .mu.m2 and 3260 .mu.m3. The packing density of nexuses is 48/1000 .mu.m2 of cell surface or .apprx. 244/muscle cell. Nexuses range in area from < 0.1 to .apprx. 1.5 .mu.m2 and they occupy 0.212% of the cell surface. The average packing density of intramembrane particles or pits in nexuses is .apprx. 7200/.mu.m2 of nexal surface, indicating that there may be .apprx. 77,000 intercellular channels in the full complement of nexuses of 1 muscle cell.