Fine structure and cytochemistry of the endoplasmic reticulum and its association with the plasma membrane of Leishmania mexicana amazonensis.

Promastigotes of Leishmania mexicana amazonensis possess an elaborated system of cytoplasmic membranes which is clearly visualized when the cells are fixed in a glutaraldehyde solution containing Ca++ and post-fixed in an osmium tetroxide solution containing Ca++ and potassium ferricyanide. When the parasites are incubated in a medium containing glucose-6-phosphate and lead nitrate, reaction product indicative of glucose-6-phosphatase activity is seen in the membrane system confirming that it corresponds to the endoplasmic reticulum (ER). A large concentration of profiles of the ER was observed at the anterior region of the cell, close to the flagellar pocket, appearing as a 'proliferative focus'. Profiles of the ER radiate toward the periphery of the cell penetrating between the subpellicular microtubules and reaching the plasma membrane.