Activation by puff adder venom of inactive renin in normal and hypertensive rat plasma

Isolation and characterization of renin-like aspartic-proteases from Echis ocellatus venom

Three aspartic proteases (SVAPs) have been isolated from venom of the saw-scaled viper, Echis ocellatus. In confirmation of prior transcriptomic predictions, all three forms match to sequences of either of the two SVAP transcripts (EOC00051 and EOC00123), have a molecular weight of 42 kDa and possess a single N-glycan. The SVAPs act in a renin-like manner, specifically cleaving human and porcine angiotensinogen into angiotensin-1 and possess no general protease activity. Their activity is completely inhibited by the aspartyl protease inhibitor Pepstatin A.

Renin: from 'pro' to promoter

Renin is the rate-limiting enzyme in a cascade that leads to production of angiotensin II, which is perhaps our most important regulator of salt and water balance and blood pressure. In this personal perspective, I describe how I entered the renin field 33 years ago by discovering that proteases increased the level of renin activity in biological fluids, so revealing the existence of a 'pro' form of the molecule. This led me on a journey that encapsulated all of the major milestones in molecular discovery for renin. These included (1) the elucidation of the steps in renin biosynthesis, (2) the cloning of renin cDNA and its gene, (3) demonstration of the structure of the renin protein, (4) using the renin gene in the first genetic studies in hypertension, (5) finding the mechanism by which the major controller, cyclic AMP, regulates the promoter, (6) showing that a strong enhancer and its weak promoter control this physiologically regulatable gene in accord with the variegation (on/off switching) model, and (7) being the first to identify molecules involved in posttranscriptional control. The renin molecule, its gene and molecular control are now very well understood, but more fine details on the topic of renin continue to emerge to delight 'reninologists' and others.

Active and inactive renin in the plasma of the snake bothrops jararaca

1. Complementing the work of Gervitz R. K., Hiraichi E., Fichman M. and Lavras A. A. C. Comp. Biochem. Physiol. 86A, 503-507 (1987), conditions have been established for measuring plasma renin activity (PRA) of the venomous snake Bothrops jararaca (Bj). 2. It corresponded to 115.9 +/- 11.5 ng equivalents of angiotensin II (AII) per ml of plasma (N = 13). 3. PRA did not increase when Bj plasma was submitted to acid-cryo-trypsin Bitis arietans venom activation of inactive renin. 4. This may indicate either absence of inactive renin in this plasma or lack of its activation, due to the already demonstrated (Nahas L., Kamiguti A. S., Betti F., Martins I. S. S. and Rodrigues M. I., Comp. Biochem. Physiol. 69A, 739-743, 1981; Prezoto B. C., Hiraichi E., Abdalla F. M. F. and Picarelli Z. P., Comp. Biochem. Physiol. 99C, 135-139, 1991) absence of factor XII.

Independent change of plasma and tissue renin in response to anesthetics

It was the purpose of this study to determine whether acute increases of endogenous plasma renin induced by administration of anesthetics cause simultaneous increases of the enzyme in aortic tissue of the rat. Administration of CO2 did not alter plasma or tissue renin. Ether, Innovar and Nembutal increased active plasma renin and had variable effects on the inactive form of the enzyme. Only Innovar, a combination of droperidol and fentanyl, increased aortic renin. The active component of Innovar was shown to be droperidol, which also increased aortic renin in 24 hour nephrectomized animals. The increase of aortic renin was, therefore, independent of changes of circulating active or inactive renin. The increase of tissue renin following droperidol was rapid, suggesting activation of an inactive tissue renin.