Morphological characteristics of a transplantable nephroblastoma (NB-Y) in F344 rats and the relation of tumour growth to hyper-reninaemia in NB-Y-bearing rats.

A transplantable tumour, designated NB-Y, was established from a spontaneous nephroblastoma in an F344 rat. NB-Y was serially passaged in syngeneic rats by subcutaneous implantation up to the 49th generation. The transplants grew into nodules with an average diameter of 5 cm and average weight of 92.9 g 4 weeks after implantation. The primary tumour and NB-Y consisted mainly of sheets or clusters of undifferentiated blastemal cells, which reacted immunohistochemically for vimentin but not for keratin. Renin-containing cells were observed in the small blood vessel walls within the primary tumour, but neoplastic cells of both primary tumour and NB-Y failed to stain for renin. Plasma renin activity was significantly higher (40.7 ng per ml per h) in transplanted rats 4 weeks after implantation compared with non-transplanted controls (28.0 ng per ml per h). Hyperplastic juxtaglomerular cells were often observed in rats bearing NB-Y. Sinusoidal dilatation was present in the liver, adrenal glands, pituitary gland and bone marrow of recipients, suggesting abnormal blood flow provoked via the renin-angiotensin system. The present study revealed the development of hyper-reninaemia in NB-Y-bearing rats, but its pathogenesis remains unknown.