Juxtaglomerular angiotensin II formation.
Previous studies have indicated the existence of an unknown AII-forming enzyme (AFE) in the glomerular region. This investigation was undertaken to characterize this enzyme further and to elucidate its possible physiologic role. AFE activity was found in cortical tissue and in microdissected superficial and juxtamedullary glomeruli but not in renal medulla. It could be blocked by the converting enzyme (CE) inhibitors SQ 20881 (133.5 micrograms/ml; 70%), SQ 14225 (20 ng/ml; 80%), and DFP (20 micrograms/ml; 80%). In contrast to AI CE, AFE was neither blocked by EDTA nor stimulated by sodium chloride. In a further study, AFE activity and AII immunoreactivity were measured simultaneously in different renal structures and in plasma under control conditions and following water deprivation. Highest AII immunoreactivity was demonstrated in microdissected glomeruli (about 10 ng/g; N = 11) and lower amounts in cortical tissue (2.83 +/- 0.72 ng/g; N = 12), avascular cortical tissue (1.80 +/- 1.08 ng/g; N = 3), outer medulla (1.52 +/- 0.33 ng/g; N = 12), inner medulla (0.72 +/- 0.17 ng/g; N = 2), and in plasma (0.212 +/- 0.066 ng/ml; N = 12). Water deprivation had no measurable effect on AFE activity; but AII immunoreactivity increased significantly in all samples. This indicates that, in spite of the extremely high juxtaglomerular renin activity, AFE cannot be regarded as the limiting enzyme for local AII formation under the conditions investigated.
D000804:Angiotensin II / Q000032:analysis / Q000096:biosynthesis*; D000818:Animals; D007606:Juxtaglomerular Apparatus / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013722:Teprotide
D009842:Oligopeptides; D000804:Angiotensin II; D013722:Teprotide