Effect of paraquat on serum angiotensin converting enzyme.

Intraperitoneal administration of paraquat to mice produced a linear dose-response increase (20 to 50 mg/kg of body weight) in serum angiotensin converting enzyme (ACE). The peak increase (31%) in ACE occurred after 50 mg/kg of paraquat and began at approximately 4 h. ACE was still significantly elevated 8 h after the administration of paraquat, but it began to return to normal 24 h later. Although serum ACE increased during the first 5 h after the administration of paraquat, lung ACE decreased. The enzyme that we measured in mouse serum was inhibited 100% by 10(-7) M of SQ 20881, a known ACE inhibitor.