1. Plasma samples from 31 normal subjects were treated (at 4°C, pH 7.0, for 2 min) with different concentrations of trypsin (500, 1000, 2000, 3000 and 4000 μg/ml) in order to assess which concentration yielded the maximum activation of inactive renin.

2. Endogenous antitryptic activity was also measured in all samples; the mean value ± sd (in μg of trypsin inhibited by 1 ml of plasma) was 953 ± 550 μg/ml (range 34–1800 μg/ml).

3. In the entire group of subjects the values of trypsin-activated renin measured with trypsin at 2000 μg/ml were significantly higher than those obtained with lower or higher trypsin concentrations.

4. With subjects divided into subgroups according to their endogenous anti-tryptic activity, the maximum yield of activation was reached with trypsin at 2000 μg/ml.

5. No significant correlations were found between single values of active, inactive or trypsin-activated renin and the corresponding levels of endogenous anti-tryptic activity. However, a weak but significant correlation (r = 0.39, P < 0.05) was found between single values of anti-tryptic activity and the corresponding percentage of activation of inactive renin.

6. Thus the maximum activation of inactive renin at 4°C for 2 min is obtained with trypsin at 2000 μg/ml independently of the corresponding endogenous anti-tryptic activity. It is not excluded that the content of protease inhibitors in human plasma might affect the proportion in vivo of circulating active and inactive renin.

This content is only available as a PDF.
You do not currently have access to this content.