Previous micropuncture studies have reported nanomolar concentrations of angiotensin II in
proximal tubular fluid and have indicated that angiotensin II or a precursor may be secreted
into the tubular lumen. Further experiments were performed to determine if proximal tubular
fluid angiotensin I concentrations are also greater than plasma and kidney levels and to
estimate the degree of intrarenal compartmentalization of the angiotensin peptides. Free-
flow proximal tubular fluid samples were collected in micropipets and were pooled for each …