Subrenal capsule assay to test the viability of parenterally delivered müllerian inhibiting substance

Abstract

Production of bovine müllerian inhibiting substance (MIS) has been increased to allow generation of large quantities of biologically active purified material. The limited MIS previously available allowed only pretreatment of tumors prior to colony inhibition or implanting in nude mice. In preparation for posttransplantation tumor treatment, a subrenal capsule assay, which was first used against human tumors heterotransplanted into nude mice and subsequently against those heterotransplanted into immunocompetent mice, was adapted to determine (1) if MIS preparations could traverse the bloodstream without degradation and (2) the optimal dose required to produce a biologic effect. Urogenital ridges from female 14-day-old rat embryos were transferred atraumatically to small pouches beneath the renal capsule of the immunocompetent male CDF, mice. The cranial-caudal orientation of the ridge with its müllerian duct was maintained. Over the next 72 hours, the mice were injected via the tail vein with 0.1 mL of an MIS-containing solution over a 100-fold concentration range. After three days, the kidneys were removed and shaved just below the ridge, which was then placed in solft agar for orientration and subsequent serial sectioning. After fixation, dehydration, and paraffin embedding, sections were stained and reeression of the müllerian duct was graded and compared according to concentration and number of MIS doses administered. Regression diminished from almost complete (4+) at the highest dose, to minimal (1 to 2+) at 1/100 of that dose. Heat-inactivated and vehicle controls caused no regression of the müllerian ducts. Müllerian inhibiting substance maintains its biologic activity in the adult mouse blood stream and exerts its effect against the transplanted embryonic rat müllerian duct; it therefore can be tested against similarly placed human tumors. The subrenal site can find many applications in the study of embryonic interactions, particularly those where neovascularization is an important prerequisite.