Renin substrate

D Le-Nguyen, A Heitz, B Castro. Renin substrates. Part 2. Rapid solid phase synthesis of the ratine sequence tetradecapeptide using BOP reagent. J Chem Soc Perkin Trans 1 1915, 1987. 

The site of formation of renin is not known, although the indirect and circumstantial evidence favors slightly the juxtaglomerular apparatus rather than the tubules as a source (18). Crude renin, however, is extracted readily from renal cortex by saline extraction, acidification, and precipitation with ammonium sulfate and sodium chloride. Other active protein substances are likewise extracted, and their separation from renin is often a matter of considerable difficulty. The renin substrate, an arglobulin, is found in blood serum and is probably formed by the liver. It can be easily salted out of beef serum as a crude preparation. 

For the tetradecapeptide (Figure 5), renin substrate, overall ion signal is lower and the protonated molecular ion is less than 50% relative abundance. Extensive fragmentation is observed in... 

Figure 5. Molecular ion region of the positive ion spectrum of Renin Substrate.

To obtain the maximum rate of renin activity, saturating amounts of the renin substrate, angiotensinogen, should be present in the reaction system. In most procedures, however, the only substrate provided is that present in the test plasma, and its concentration can be quite variable. According to some investigators, PRA is best estimated when the plasma specimen is incubated with an excess of exogenous renin substrate prepared from nephrectomized human subjects, oxen, or sheep. This type of assay is usually known as a plasma renin concentration assay rather than PRA assay. Unfortunately the measured renin depends on the source and concentration of the renin substrate. Synthetic peptides that resemble the M-terminal portion of angiotensinogen have also been used as renin substrates, but these substances can be hydrolyzed by nonspecific plasma proteases. 

Initial design of the inhibitors was based on a rational design strategy using the renin substrate as a starting point. Some of the early studies indicated that the octapeptide of horse angiotensinogen (His-Pro-Phe-His-Leu-Leu-Val-Tyr), cleaved slowly by renin between the two leucine residues, was a weak competitive inhibitor of renin. This led to the modifications in the P, and P, positions (Leu-Leu) of this peptide. The early work indicated that the two leucine residues could be replaced by... 

These ideas, then, became the strategy for the design for numerous peptoids resembling known renin substrates. The scissile dipeptide was replaced with nonscissile statine and analogous amino acids such as 4-amino-5-cyclohexyl-3-hydoxypentanoic acid (ACHPA) and fluorostatinone to act as presumed transition-state analogs and to become potent renin inhibitors. 

Estrogens can cause nausea, breast tenderness, and hyperpigmentation. They can also cause or exacerbate migraine headaches, hypertension (due to an increased level of renin substrate), and cholestasis. 

A number of recent reviews describe topics related to hypertension. The significance of catecholamine levels in hypertension has been discussed and a cautionary note offered that levels in mixed venous blood are unreliable Indicators of sympathetic neural activity in hypertension. The role of the S5nnpathoadrenal axis in hypertension has been reviewed. The need for intact vascular endothelium for vascular responses to a number of agents has been described. A recent review examines the role of renin substrate in hypertension. Lastly, based on the unlmodal distribution of blood pressures, the existence of hypertension as an entity has been questioned. ... 

The renin substrate has been adapted to a time point format on 96-well microtiter plate fluorescence reader for high-throughput data generation. This format has been used to examine the effect of a series of reagents (DMSO, high salt, DTT, etc.) on the stability and activity of recombinant human renin. 

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