Proximal tubule tendrils: fact or artefact

Tendrils have been reported to radiate from luminal surfaces of proximal tubules in rat kidneys by Andrews and Porter ('74) using scanning microscopy, but they were not seen by Bulger et al. ('74). In this study, the perfusion procedure of Andrews and Porter was re-investigated. Tendrils were found only in regions which had characteristics of poor fixation. They were especially prominent if the perfusion pressure was purposely allowed to fall and subsequently increased to re-expand the tubules. The tendrils could then be seen in all portions of the proximal convoluted tubule and not exclusively in the initial portion as previously reported.