We compared the effectiveness of two techniques involving the use of the enzyme trypsin to activate inactive renin in human plasma. Both these methods were developed to optimize activation with trypsin by preventing the possible destruction of activated renin by trypsin itself. In one method, an antitryptic agent such as benzamidine is added to plasma, concomitantly with trypsin (liquid phase). In the other a low concentration of Sepharose-bound (immobilized) trypsin is used. In six plasma samples we have found that trypsin (1.5 mg/ ml) activation, with or without benzamidine (0.8 mg/ml), yielded similar values of activated renin (11.0 ± 2.7 vs. 11.3 ± 2.3 ng/ml/hr). However, the addition of immobilized trypsin to pool plasma pretreated with trypsin plus benzamidine caused a further increase in plasma renin activity (PRA); in contrast, the addition of trypsin and benzamidine to pool plasma pretreated with immobilized trypsin caused a decrease in PRA. In 17 plasma samples from patients with essential hypertension we found that the inactive renin values were always higher after treatment with immobilized trypsin than with trypsin plus benzamidine (9.0 ± 0.7 vs. 6.1 ± 0.5 ng/ml/hr, P <0.01); moreover, there was a positive correlation between the differences in the values of inactive renin measured with the two methods and the values obtained with immobilized trypsin (r = 0.64, P <0.01). Therefore, the activation with immobilized trypsin is more effective than that with liquid-phase trypsin, alone or in combination with benzamidine, in converting inactive renin in human plasma. It appears that with the method using liquid-phase trypsin the degree of underestimation in the measurement of the inactive enzyme is proportional, in absolute values, to its plasma concentration.
|Number of pages||5|
|Journal||The Journal of Laboratory and Clinical Medicine|
|Publication status||Published - 1987|
ASJC Scopus subject areas
- Pathology and Forensic Medicine