title: Trypsin-activatable inactive renin in rat plasma.
abstract: 1. Activation of inactive renin in rat plasma has been studied with different trypsin concentrations and incubation times at pH 6.2 and 4 degrees C. 2. Trypsin concentrations below 2 mg/ml, lower than endogenous rat plasma anti-trypsin activity, do not activate inactive renin, whereas maximal activation is obtained with trypsin at 6 mg/ml for 1 min at 4 degrees C, pH 6.2. 3. Under these conditions trypsin can cleave dialysable fragments from renin substrate. ANG I can be generated at 37 degrees C with a pH optimum of 5.3. Nevertheless, the ANG I formation at pH 6.2 was totally unaffected. 4. Incubations longer than 2 min with trypsin at 6 mg/ml can induce a direct cleavage of dialysable ANG I-containing fragments strongly interfering with the measurements of renin activity at pH 6.2. 5. On average 40% of the total renin measured in plasma of normotensive WK rats is in the inactive form, although a wide range of variation is observed.
mesh_terms: D000803:Angiotensin I / Q000096:biosynthesis; D000818:Animals; D003080:Cold Temperature; D003956:Dialysis; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012083:Renin / Q000097:blood*; D014357:Trypsin / Q000494:pharmacology*
chemical_list: D000803:Angiotensin I; D014357:Trypsin; D012083:Renin