Dog inactive renin: biochemical characterization and secretion into renal plasma and lymph

It has been suggested that the dog is a useful model for studies of inactive renin (IR). However, the nature and origin of the trypsin-activated angiotensin-forming activity in dog plasma have not been fully defined. We characterized dog IR using renin-specific antibody, immunoaffinity, and Affigel blue chromatography. Activated IR resembles renal and plasma active renin in biochemical and immunological properties. IR was detected in renal lymph, arterial and venous plasma, as well as renal extracts. At basal state, there was a significant renal venous-arterial gradient of IR indicating secretion from the kidney. Furthermore, a sixfold higher concentration of IR was demonstrated in renal lymph than in plasma. Our data provides evidence for two possible routes of IR secretion from the kidney and supports the contention that the dog is a good model for studies of IR secretion and regulation.