Rat renal and plasma prorenin are activated in vitro by different mechanisms.
The aim of the present study was to purify and identify a plasma protein fraction (PreR-Co) involved in renal prorenin activation and to explore its capacity to process plasma prorenin. PreR-Co was obtained from plasma as a single electrophoretic band by (NH(4))(2)SO(4) precipitation, Sephacryl S-200 HR gel filtration, anti-rat albumin immunoaffinity, and ion-exchange chromatography. The amidase, esterase, and kallikrein activities of PreR-Co were studied, as was its N-terminal amino acid sequence. Rat kidney extract or plasma (normal or previously treated with acid to pH 2.8) were incubated with PreR-Co for 15 minutes at 37 degrees C. Renin concentration was measured by incubation with homologous angiotensinogen. The same protocol was repeated with samples activated by trypsin. The N-terminal amino acid sequence was IIGGSMDAKGSFP, which had a homology of 90% with the beta-chain of haptoglobin, 69% with serine-proteases, and 65% with kallikreins. The renin concentration in rat kidney extract was 34+/-4 ng of angiotensin I (Ang I). mg of tissue(-1). h(-1). After PreR-Co or trypsin treatments, renin concentrations were 211+/-7 and 110+/-11 ng of Ang I. mg of tissue(-1). h(-1), respectively. The plasma renin concentration in normal plasma was 67.6+/-13.3 ng of Ang I. mL(-1). h(-1), and no significant difference was observed after PreR-Co treatment. However, a significant increase (202.8+/-7.8 ng of Ang I. mL(-1). h(-1); P<0.01) was found after trypsin treatment. The isolated PreR-Co acts on renal prorenin but not on plasma prorenin. These results suggest that active renin is processed in the kidney by a circulating enzyme that may have a role in the regulation of circulating renin.
Vincent
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PA
Instituto Superior de Investigaciones Biológicas (INSIBIO), Universidad Nacional de Tucumán and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), San Miguel de Tucumán, Argentina.
De Vito
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D000581:Amidohydrolases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001798:Blood Proteins / Q000302:isolation & purification; D010450:Endopeptidases / Q000097:blood* / Q000302:isolation & purification; D004792:Enzyme Precursors / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D004950:Esterases / Q000378:metabolism; D005260:Female; D007610:Kallikreins / Q000378:metabolism; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D051381:Rats; D017207:Rats, Sprague-Dawley; D012083:Renin / Q000097:blood* / Q000737:chemistry / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000502:physiology; D017421:Sequence Analysis
D001798:Blood Proteins; D004792:Enzyme Precursors; D004950:Esterases; D010450:Endopeptidases; D007610:Kallikreins; D012083:Renin; C453579:PreR-Co; D000581:Amidohydrolases; C019665:amidase