ENZYME-LINKED-IMMUNOSORBENT-ASSAY FOR ANGIOTENSIN-CONVERTING ENZYME IN RAT TESTES

An enzyme-linked immunosorbent assay (ELISA) was developed to determin e the concentration of angiotensin-converting enzyme (ACE) in the test es of rats. ACE was isolated and purified from the testes by affinity chromatography using the specific ACE inhibitor lisinopril bound to Se pharose CL-4B. Polyclonal antibodies to the purified ACE protein were produced in rabbits. A competitive antigen capture ELISA was developed by using antibody-coated polystyrene tubes as the solid phase and alk aline phosphatase covalently bound to purified ACE as the detector. Th is paper describes in detail the procedures for preparing the affinity gel and column, isolating and purifying A CE protein, producing and i solating the antibodies, production of the alkaline phosphatase-ACE co njugate, and the development of the ELISA. The assay was tested by det ermining the amount of ACE protein in rat testis as affected by zinc d eficiency, a condition known to reduce ACE activity in this tissue. Pr eliminary results showed a direct correlation between the reduction in ACE activity and ACE protein in the Zn-deficient rats.