An insect epidermal cell line (UMBGE-4): Structural and electrophysiological characterization

Abstract

1. 1. The cellular organization (including junctional connectivity) and electrophysiological characteristics of the UMBGE-4 epithelial cell line originally derived from the cockroach were studied. These cells grew in culture in the form of hollow vesicles which could reach 5 mm in diameter. The wall of the vesicles varied in form and thickness from resembling a squamous to a columnar epithelium. Parts of the vesicle wall were multi-cellular with some cytoplasmic variability in the constituent cells. On the whole, the cellular architecture of the vesicles resembled that of a secretary epithelium with abundant microvilli and apical vacuoles, an extensive network of endoplasmic reticulum and prominent Golgi apparatus. 2. 2. The main type of cell junction was septate-like and comprised extensive, convoluted regions of cellular apposition with some gap junctions therein. The septate junctions were permeated extensively by lanthanum and the epithelium appeared to be leaky. 3. 3. A small negative trans-cellular (lumen) potential (mean value, −2.7 mV) was present and this was only transiently affected by changes in extracelluar Na +, K + or Cl − concentrations. 4. 4. The cells' resting membrane potentials were distributed normally around a mean of − 77 mV. Some 64% of resting membrane electrogenesis could be accounted for in terms of K + and Cl − permeabilities; Na + had no involvement. 5. 5. The structural, electrophysiological and biochemical characteristics taken together would suggest that the UMBGE-4 cells could serve as a useful model for the epidermal epithelium in insects.