Determination of plasma total renin level by RIA with a monoclonal antibody: Value as a marker for nephroblastoma

Plasma total renin is a new, useful marker for nephroblastoma, but the conventional method for determining its level is sophisticated and requires large blood samples. To develop a simpler technique, a monoclonal antibody specific for both inactive and active renin (inactive + active = total) was raised, and a radioimmunoassay (RIA) system was established. This monoclonal antibody stains only the juxtaglomerular apparatus; values determined by this RIA did not change before and after activation. So far, the RIA system has been applied to 136 samples from 92 patients. Plasma total renin levels were also determined with the conventional method: samples were activated, then renin activity was assayed by measuring angiotensin I. The coefficient of the data obtained by these two different techniques was 0.921 (P less than .01). Plasma total renin levels in patients with nephroblastoma were significantly increased (546.5 +/- 297.8 pg/mL) over those in patients with neuroblastoma (218.6 +/- 46.5 pg/mL) and in controls (165.8 +/- 67.5 pg/mL, P less than .01). After removal of Wilms' tumors, the levels decreased to normal when sampled every 2 weeks. It was concluded that a newly developed RIA system is more useful in determining plasma total renin levels in patients with nephroblastoma.