Continuity of intercellular space and endoplasmic reticulum of keratinocytes

Intracytoplasmic vacuoles were produced within keratinocytes of the epidermis by hypertonic solutions of sodium chloride, dextrose, and human albumin injected into the dermis of guinea pigs. They arose from a canalicular system which unfolded at higher osmolarities; the degree of unfolding was related to the degree of hyperosmolarity chosen. Tracers (horseradish peroxidase and colloidal silver) incorporated into the test solutions freely permeated the cisternal system and the vacuoles, demonstrating their continuity with the intercellular space. The membranes lining this cisternal system were not stained by ruthenium red and exhibited no nucleosidetriphosphatase activity which indicated that they did not represent infoldings of the plasma membrane; they were impregnated by the osmium soaking technique (which stains endoplasmic reticulum) and their dimensions were identical with those of the outer nuclear membrane and endoplasmic reticulum. It is concluded that a continuity exists between endoplasmic reticulum of keratinocytes and extracellular compartment which unfolds under hyperosmolar conditions. Since endoplasmic reticulum and perinuclear space are continuous the continuity of plasma membrane and endoplasmic reticulum, as demonstrated in this paper, suggest the existence of a potential path for the exchange of substances and information between the nuclear membrane and the extracellular compartment.