The versatile stellate cell - more than just a space-filler.

Most epithelia contain multiple cell types that interact to perform the roles required of the tissue. In insect epithelia, the apical plasma membrane V-ATPase dominates ion-transport models, and (as in vertebrates) is usually found in specialized intercalated cell types or regions. The Malpighian tubules of several insect Orders contain not just a mitochondrion-rich principal cell expressing high levels of V-ATPase, but a smaller, intercalated "type II", "secondary" or "stellate" cell. Recent data show that this cell type plays a key role in control of chloride and water flux across the tissue, but also may play other, still unsuspected dynamic roles.