Effectiveness of Sepharose-bound trypsin versus liquid-phase trypsin plus benzamidine for activation of inactive renin in human plasma
Morganti, A.; Sala, C.; Turolo, L.; Auxilia, F.; Cianci, L.; Checchini, M.; Zanchetti, A.
Journal of Laboratory and Clinical Medicine 109(1): 13-18
1987
ISSN/ISBN: 0022-2143 PMID: 3540163 Document Number: 295909
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 less than 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 less than 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.