Permeability of the podocytes of Lumbricus terrestris (Annelida, Oligochaeta) to different markers

Abstract

 The distribution of different injected markers between blood vessels and the coelomic cavity of Lumbricus terrestris was investigated by light and electron microscopy in order to show the direction of filtration and the permeability of the basement membrane of podocytes. The present results revealed that ultrafiltration takes place across the ventral vessel as well as through the peri-intestinal blood sinus of the typhlosolis. Furthermore, the filtration processes seem to be restricted to the front part of the body. Fluorescein isothiocyanate (FITC) [molecular weight (MW) 389.4 Da], Procion yellow (MW 873 Da), FITC-labelled dextrans (MW 39 kDa) and gold particles up to a diameter of 10–12 nm passed the podocytes. Evans blue (MW 960.8 Da) could not permeate through the podocytes. The injected gold particles were found inside the extracellular channels of the podocyte, between the microvilli-like processes of the podocyte and on the coelomic side of the peritoneal epithelium. The appearance of gold particles in the previously described structures indicated that filtration takes place from the lumen of the ventral vessel to the coelomic cavity.