Characterization of a radioimmunoassay to determine plasma total renin

Long-term preservation of renin-secreting ability by human adult juxtaglomerular tumor cells in explant culture

Studies on cultured human renin(R)-producing tumors cells are few. In this work the R secretion by a human juxtaglomerular tumor (JGT) in various tissue culture models was evaluated by a new immunoradiometric assay. Freshly isolated JGT cells actively secreted total R (tR; about 70% of which is proR) into the perfusion media of very short-term cultures (tR concentration, 100-400 ng/ml/10(6) cells), independently of factors stimulating or inhibiting R output by normal JG cells. Primary monolayer cultures of the same JGT rapidly lost their tR-secreting capability and died by apoptosis within two months. Conversely, a JGT explant survived for up to 22 months in vitro. During the first year of culture, this explant increased in volume and generated, at 3- to 4-monthly intervals, several self-limited cellular outgrowths, from which it became detached. Meanwhile, tR secretion by the explant decreased very slowly, though its decline was transiently and partly reversed by various combinations of growth factors, hormones, a prostaglandin, and selenous acid added to either a serum-enriched or a synthetic medium. By the 12th month in vitro, tR secretion had faded away. Like the primary monolayers, the various explant outgrowths, once detached, stopped secreting tR and died in a few weeks. Hence, the preservation of a histiotypic relationship and the actions of several mitogenic and/or differentiating agents are essential for the long-term survival and the continuance of R secretion by human JGT cells in vitro.

Renin production in congenital mesoblastic nephroma in comparison with that in Wilms' tumor

The case of an infant with congenital mesoblastic nephroma and associated reninism is presented. The patient was a 39-day-old boy who presented with a left abdominal mass and mild hypertension (112/70 mm Hg). Both plasma renin activity (PRA) and plasma total renin concentration (PTRC) were elevated; the PTRC value of 1458 pg/mL of this case was the highest we had seen in patients with childhood renal tumors. The tumor was successfully removed and histologically confirmed as a congenital mesoblastic nephroma (cellular variant). The patient's PRA and PTRC returned to normal after nephrectomy. Indirect immunoperoxidase staining showed renin localized predominantly in the juxtaglomerular apparatuses adjacent to the glomeruli entrapped by the tumor. No positive staining was seen in the tumor cells. These findings indicate that the entrapped glomeruli may play a significant role in producing renin. More important, PTRC was extremely high compared to the moderate increase of PRA and to the mild elevation of blood pressure. The mechanism of renin production by childhood renal tumors is discussed, and the importance of studying inactive renin and total renin is emphasized.