The anionic charge barrier in the renal corpuscle of the pronephros in the lamprey, Petromyzon marinus L.

The charge barrier within the renal corpuscle of the pronephric kidney of the lamprey, Petromyzon marinus, was investigated at two life cycle intervals using cationized ferritin and polyethyleneimine. In the larval renal corpuscle the endothelium of the glomerular capillaries and the laminae rarae externa and interna of the glomerular basement membrane show regularly-spaced deposits of the tracers. The lamina densa remains unstained. Concomitant with a loss of major processes of the visceral epithelial podocytes and development of an extensive mesangial matrix in late adult life are alterations in the distribution of the anionic sites. The lamina rara interna is no longer a distinct entity and the mesangium contains irregularly-distributed anionic sites surrounding electron-dense deposits. The results indicate that the distribution of the anionic sites during adult life most likely affects the ability of the renal corpuscle to act as an efficient filtration device. This charge distribution is consistent with that seen during some renal pathologies of higher vertebrates.