[Evidence for existence of pores in intramembranous particles revealed by freeze fracturing].

In freeze-fracture replicas of membranes (plasma and intracellular) in a variety of animal cells, it is possible to detect the presence of intramembrane particles containing an electron-dense spot. The spot is interpreted as an accumulation of platinum into a cavity; the cavity could in turn correspond to a hydrophilic pore in the particle.