Short-Lived Active Prorenin: Precursor of So-Called Native Prorenin.

The enzymatic activity of the aspartic protease, renin, is critical for its function in blood pressure regulation and sodium homeostasis. Incubation of so-called native prorenin at low pH leads to its activation. After binding to transition-state mimicking renin inhibitors at neutral pH, prorenin attains the active conformation, as indicated by immunosorbent assay using monoclonal antibodies specific for epitopes of the prosegment or the renin body. A comparison of immunosorbent assay with enzyme-kinetic assay revealed the intermediary steps of prorenin auto-activation/inactivation. The kinetically identified intermediary steps of activation/inactivation correspond with the published crystal structures of free renin, free prorenin, and renin in complex with inhibitors. Both renin and activated prorenin exist in 2 forms, α and ß. The α form is active, and the α/ß quantity ratio is 2.5. The kidney produces renin and prorenin, while the ovarium, placenta, and eye produce inactive prorenin. The production of renin by these organs has never been demonstrated. We propose that the so-called native prorenin in extracellular fluid, including the circulation, is derived, at least partly, from short-lived active prorenin. Its potential paracrine function is discussed.

Arterial stiffness and risk of coronary heart disease and stroke: the Rotterdam Study.

BACKGROUND: Arterial stiffness has been associated with the risk of cardiovascular disease in selected groups of patients. We evaluated whether arterial stiffness is a predictor of coronary heart disease and stroke in a population-based study among apparently healthy subjects. METHODS AND RESULTS: The present study included 2835 subjects participating in the third examination phase of the Rotterdam Study. Arterial stiffness was measured as aortic pulse wave velocity and carotid distensibility. Cox proportional hazards regression analysis was performed to compute hazard ratios. During follow-up, 101 subjects developed coronary heart disease (mean follow-up period, 4.1 years), and 63 subjects developed a stroke (mean follow-up period, 3.2 years). The risk of cardiovascular disease increased with increasing aortic pulse wave velocity index. Hazard ratios and corresponding 95% CIs of coronary heart disease for subjects in the second and third tertiles of the aortic pulse wave velocity index compared with subjects in the reference category were 1.72 (0.91 to 3.24) and 2.45 (1.29 to 4.66), respectively, after adjustment for age, gender, mean arterial pressure, and heart rate. Corresponding estimates for stroke were 1.22 (0.55 to 2.70) and 2.28 (1.05 to 4.96). Estimates decreased only slightly after adjustment for cardiovascular risk factors, carotid intima-media thickness, the ankle-arm index, and pulse pressure. The aortic pulse wave velocity index provided additional predictive value above cardiovascular risk factors, measures of atherosclerosis, and pulse pressure. Carotid distensibility as measured in this study was not independently associated with cardiovascular disease. CONCLUSIONS: Aortic pulse wave velocity is an independent predictor of coronary heart disease and stroke in apparently healthy subjects.

A local pre-receptor mechanism of hormone stimulus amplification: focus on angiotensin II in resistance blood vessels.

BACKGROUND: The in-vivo correlation between vascular tone and the concentration of free angiotensin (Ang) II at the level of the arterioles, under (patho)physiological conditions, is not known. OBJECTIVE: To examine the in-vivo kinetics of binding of Ang II to Ang II type 1 (AT1) receptors in vascular tissue. METHODS AND RESULTS: A plane vascular smooth muscle (VSM) sheet containing a single layer of cells, at one side exposed to Ang II, was the starting point for designing a mathematical model based on local receptor density and geometric considerations and on kinetic parameters of Ang II diffusion and Ang II-AT1 receptor complex formation and internalization. Calculations demonstrate that a diffusing Ang II molecule at short distance from the receptor has an almost 100% chance to be actually bound, so that the apparent binding rate constant (per unit of receptor concentration) is greatly augmented. This pre-receptor stimulus amplification (PRESTAMP) mechanism is sustained by AT1 receptor-mediated endocytosis and receptor recycling. On the other hand, PRESTAMP also enhances endocytotic receptor downregulation, and calculations predict that steady-state levels of Ang II above threshold have relatively little additional effect. CONCLUSION: The results explain why physiological concentrations of free Ang II far below the equilibrium dissociation constant of its reaction with AT1 receptors are sufficient to increase vascular resistance, and why a correlation between blood pressure and the concentration of free Ang II is often difficult to demonstrate.

Arterial stiffness as the candidate underlying mechanism for postural blood pressure changes and orthostatic hypotension in older adults: the Rotterdam Study.

OBJECTIVE: To investigate whether arterial stiffening, one of the characteristics of the aging vascular system, is associated with orthostatic hypotension. DESIGN: Cross-sectional data of a cohort study in elderly men and women. PARTICIPANTS: We investigated the relationship between arterial stiffness and orthostatic hypotension within the framework of the Rotterdam Study, a population-based study in individuals aged 55 and older. The present study included 3362 subjects participating in the third examination phase. The carotid-femoral pulse wave velocity was used as measure of arterial stiffness. Orthostatic hypotension was assessed with blood pressure measurements in supine and standing position. RESULTS: Odds ratios for orthostatic hypotension increased through quartiles of pulse wave velocity; the age, gender and mean arterial pressure adjusted odds ratio in the last quartile of pulse wave velocity was 1.45 (95% confidence interval, 1.09-1.93) when compared with the first quartile (reference). In fully adjusted models estimates remained statistically significant. In subjects with higher stiffness we observed a higher drop in blood pressure but no significant change of heart rate. CONCLUSIONS: Arterial stiffness is independently associated with orthostatic hypotension. The drop in blood pressure levels and the contemporary attenuated response of heart rate to orthostatic challenge in subjects with stiffer arteries support the hypothesis that arterial stiffness may explain, at least in part, the reduced baroreflex observed in older adults.

Adrenal angiotensin: origin and site of generation.

BACKGROUND: Circulating angiotensin (Ang) II accumulates in adrenal tissue via binding to Ang II type 1 (AT1) receptors, reaching levels that are 15 to 20 times higher than in blood. Adrenal tissue contains a second renin transcript that gives rise to a truncated prorenin representing a cytosolic form of renin. Here we investigated what percentage of adrenal Ang II originates at adrenal tissue sites, and whether intracellular renin contributes to adrenal angiotensin production. METHODS: Concentrations of endogenous and iodine-125 (125I)-labeled Ang I and II were measured in adrenal tissue and blood from pigs after 125I-Ang I infusion. RESULTS: In the adrenal tissue in all animals, 125I-Ang I was undetectable. In untreated pigs, adrenal 125I-Ang II was 17 +/- 1 times arterial 125I-Ang II, and tissue Ang I and II were 5 +/- 1 and 388 +/- 40 times higher than plasma Ang I and II. The AT1 receptor antagonist eprosartan reduced adrenal 125I-Ang II accumulation by 80%, and increased plasma Ang II to a greater degree than tissue Ang II. As a consequence, eprosartan equally reduced the tissue/plasma concentration ratios of both Ang II and 125I-Ang II. Captopril did not alter 125I-Ang II accumulation, and acutely, but not chronically, reduced the adrenal Ang II/I ratio. CONCLUSIONS: More than 90% of adrenal Ang II originates at adrenal tissue sites. Local adrenal Ang II generation occurs extracellularly and is followed by internalization via AT1 receptor-mediated endocytosis. Enhanced angiotensin generation, combined with incomplete AT1 receptor blockade and the large adrenal AT1 receptor reserve, explains why eprosartan increased rather than decreased adrenal Ang II. Our data do not support angiotensin generation by truncated prorenin.

Moderate alcohol consumption is associated with reduced arterial stiffness in older adults: the Rotterdam study.

BACKGROUND: Light-to-moderate alcohol consumption has been associated with a lower risk of cardiovascular disease. The protective effect of alcohol could involve arterial properties as arterial stiffness and distensibility. METHODS: The relationship between alcohol and arterial stiffness was studied within the framework of the Rotterdam Study, a population-based study in individuals aged 55 and older. The present study included 3178 participants in the third examination phase. Arterial stiffness was measured by two different methods, i.e., the carotid-femoral pulse wave velocity and the DC of the common carotid artery. Categories of alcohol consumption were defined as follows: < or =3 glasses of alcohol per week, 4-10 glasses per week, 11-20 glasses per week, and > or =21 glasses per week. Linear regression analysis was used to investigate the association between alcohol consumption and measures of arterial stiffness. RESULTS: In multivariate-adjusted models, women drinking 4-10, 11-20, and > or =21 glasses of alcoholic beverage per week had a -0.07 (0.22 to -0.38), -0.18 (0.12 to -0.49), and 0.12 (0.19 to -0.43) m/s difference in mean pulse wave velocity compared to those drinking 0-3 glasses per week (reference group). Corresponding differences in the carotid DC were 0.68 (1.21 to 0.15), 0.28 (0.82 to -0.25), and 0.36 (0.91 to -0.18) 10(-3)/kPa. In men, the estimates were not statistically significant, although a similar trend was observed. CONCLUSIONS: Moderate alcohol consumption is associated with lower arterial stiffness in women independently of cardiovascular risk factors and atherosclerosis.

C-reactive protein and arterial stiffness in older adults: the Rotterdam Study.

Arterial stiffness is one of the characteristics of vascular aging. Increases in pulse pressure, which reflect an increase in the stiffness of the large arteries, are associated with elevated C-reactive protein (CRP) levels. This may suggest a role of inflammation in the development of arterial stiffness. We investigated the relation between measures of arterial stiffness and CRP within the framework of the Rotterdam Study, a population-based cohort study including subjects aged 55 years and older. The carotid-femoral pulse wave velocity and the distensibility coefficient of the carotid artery were used as measures of arterial stiffness. Data on both arterial stiffness and CRP were available for 866 participants. In adjusted models, levels of CRP were linearly associated with pulse wave velocity (regression coefficient 0.088, 95% CI 0.006-0.170). Adjusted mean values of pulse wave velocity were significantly different across tertiles of CRP, being higher in the highest tertile of CRP. However, no significant association between CRP and carotid distensibility was observed.

Angiotensin-converting enzyme gene polymorphism and common carotid stiffness. The Rotterdam study.

The insertion/deletion (I/D) polymorphism of the ACE gene may be involved in structural arterial changes. Aim of the present study was to assess the relationship between the ACE I/D gene and vessel wall stiffness among older adults. The study was conducted within the Rotterdam study, a population-based cohort study including subjects aged 55 years and older. The II, ID and DD genotypes of the ACE gene were determined in all subjects. The distensibility coefficient (10(-3)/kPa) of the carotid artery and the carotid-femoral pulse wave velocity were measured during the third phase of the Rotterdam study (1997-1999) and were used as measure of arterial stiffness. Data on both carotid stiffness and the ACE genotype were available for 3001 participants. After adjustment for age and gender, subjects with the ID and DD genotype had higher carotid stiffness compared to subjects with II genotype (distensibility coefficient (10(-3)/kPa) 10.24 (95% CI, 10.06-10.43), 10.27 (95% CI, 10.02-10.52), 10.65 (95% CI, 10.37-10.93), respectively (ID versus II genotype, P = 0.017), (DD versus II genotype, P = 0.037)). In stratified analyses, the association was strongest in subjects younger than 70 years. No difference was seen for pulse wave velocity among genotypes. In conclusion, the results of this population-based study show that the ACE ID/DD genotypes are associated with higher common carotid stiffness.

Vasoconstriction is determined by interstitial rather than circulating angiotensin II.

1. We investigated why angiotensin (Ang) I and II induce vasoconstriction with similar potencies, although Ang I-II conversion is limited. 2. Construction of concentration-response curves to Ang I and II in porcine femoral arteries, in the absence or presence of the AT(1) or AT(2) receptor antagonists irbesartan and PD123319, revealed that the approximately 2 fold difference in potency between Ang I and II was not due to stimulation of different AT receptor populations by exogenous and locally generated Ang II. 3. Measurement of Ang I and II and their metabolites at the time of vasoconstriction confirmed that, at equimolar application of Ang I and II, bath fluid Ang II during Ang I was approximately 18 times lower than during Ang II and that Ang II was by far the most important metabolite of Ang I. Tissue Ang II was 2.9+/-1.5% and 12.2+/-2.4% of the corresponding Ang I and II bath fluid levels, and was not affected by irbesartan or PD123319, suggesting that it was located extracellularly. 4. Since approximately 15% of tissue weight consists of interstitial fluid, it can be calculated that interstitial Ang II levels during Ang II resemble bath fluid Ang II levels, whereas during Ang I they are 8.8 - 27 fold higher. Consequently at equimolar application of Ang I and II, the interstitial Ang II levels differ only 2 - 4 fold. 5. Interstitial, rather than circulating Ang II determines vasoconstriction. Arterial Ang I, resulting in high interstitial Ang II levels via its local conversion by ACE, may be of greater physiological importance than arterial Ang II.

Blood pressure components and cardiovascular events in older adults: the Rotterdam study.

OBJECTIVES: To compare the strength of the relative risks of systolic (SBP) diastolic blood pressure (DBP) and pulse pressure (PP) as predictors of myocardial infarction and stroke in older adults. DESIGN: Prospective cohort study. SETTING: The Rotterdam Study, a Dutch population-based study. PARTICIPANTS: A total of 4,234 subjects aged 55 and older with no previous myocardial infarction (MI) or stroke at baseline. MEASUREMENTS: Blood pressure levels at baseline, first MI and stroke, all-cause mortality during follow-up. RESULTS: During follow-up, 205 subjects had an MI (average follow-up period 7 years), 137 subjects had a stroke (average follow-up period 6.1 years), and 748 subjects died. A 1-standard deviation difference in SBP, DBP, and PP was associated with relative risks of MI of 1.24 (95% confidence interval (CI)=1.06-1.46), 1.07 (0.92-1.25), and 1.25 (1.07-1.48), respectively. Corresponding relative risks for stroke were 1.59 (1.37-1.86), 1.27 (1.10-1.48), and 1.48 (1.27-1.72). For all-cause mortality the corresponding relative risks and 95% CI were 1.21 (1.11-1.31), 1.06 (0.99-1.14), and 1.20 (1.10-1.31). CONCLUSION: The results of this study suggest that, in a population of apparently healthy older adults, PP is not a better predictor of cardiovascular events and all-cause mortality than SBP.

Intima-media thickness of the common carotid arteries is related to coronary atherosclerosis and left ventricular hypertrophy in older adults.

Increased intima-media thickness (IMT) of the common carotid arteries is related to generalized atherosclerosis and increased risk of future myocardial infarction and cerebrovascular disease. An association between IMT and the presence of coronary artery disease (CAD) has been documented, but controversial data have been found about the relation between increased IMT and the extent of CAD. An association between carotid atherosclerosis and cardiac remodeling has also been reported. It is still unclear whether increased IMT of the common carotid arteries might be associated with prevalent cardiovascular disease in older adults. This study included 70 patients, 37 with CAD and 33 matched for age and gender without CAD. All patients underwent a baseline clinical examination, B-mode ultrasound of the carotid arteries, and echocardiography. The authors evaluated the possible association between increased IMT with the presence and extent of CAD and the presence of left ventricular hypertrophy (LVH). The patients with CAD had significantly increased IMT compared to patients without CAD. IMT was found to increase with the number of coronary vessels affected, after adjustment for age, gender, hypertension, hypercholesterolemia, diabetes mellitus, and smoking habits. The test for trend was highly significant (p<0.001). Patients with LVH had significantly increased IMT as compared with patients without LVH. IMT of the common carotid arteries was increased in the presence of CAD and increased with the number of coronary vessels diseased. Second, the authors found that IMT of the common carotid arteries was significantly increased in patients with LVH. Increased IMT, as an indicator of subclinical cardiovascular disease, may help to identify patients who would benefit from aggressive therapeutic measures.

How does the angiotensin II type 1 receptor 'trump' the type 2 receptor in blood pressure control?

BACKGROUND: A kinetic model for the binding of angiotensin II (Ang II) to AT1 receptors (AT1Rs) in arterioles did suggest a novel mechanism of association rate amplification and facilitated Ang II diffusion in vivo. AIM OF STUDY: To examine how this mechanism, acting on AT1R, will affect the stimulation of AT2R. METHOD: The model distinguishes between the diffusion of plasma Ang II across the endothelium layer (thickness 10(-4) - 5 × 10(-4) cm) into the vascular smooth muscle (VSM) layer (5 × 10(-4) cm), and the diffusion of tissue Ang II from perivascular interstitium (thickness of micromilieu fluid layer at abluminal VSM surface 10(-6) - 10(-5) cm, i.e. 1 to 10 times the glycocalyx). Thus, Ang II concentration [Ang II] is taken to be 0 at the abluminal and adluminal VSM cell surfaces, respectively. Tissue Ang II is defined as originating from local generation and/or from the capillary circulation. [Ang II]/AT1R and [Ang II]/AT2R occupancy curves for the two directions of diffusion are constructed from the model-based calculations. RESULTS: Ang II, at 10(-15)-10(-13) mol/ml (~1-100 pg/ml), is much less likely to react with vascular AT2R than AT1R, though it has similar affinity for the receptor types. With plasma [Ang II] = 10(-15)-10(-13) mol/ml, AT2R occupancy is less than 10% of maximum on endothelium, and virtually 0 on VSM, whereas AT1R occupancy on VSM is virtually 0 at plasma [Ang II] < 10(-14) mol/ml, and between 0 and 30% at plasma [Ang II] = 10(-13) mol/ml. With tissue [Ang II] = 10(-15)-10(-13) mol/ml, VSM AT2R occupancy is close to 0, whereas VSM AT1R occupancy is 40-60% in the absence of endocytotic AT1R down-regulation, and up to 70-90% in its presence. CONCLUSION: The threshold concentration of Ang II needed for response is much higher for AT2R than for AT1R. Plasma Ang II rather than tissue Ang II is the agonist of AT2R, and the reverse applies to AT1R. Thus, AT2R stimulation may come into play only at unusually high circulating levels of Ang II.

New renin inhibitor VTP-27999 alters renin immunoreactivity and does not unfold prorenin.

Renin inhibitors like aliskiren not only block renin but also bind prorenin, thereby inducing a conformational change (like the change induced by acid) allowing its recognition in a renin-specific assay. Consequently, aliskiren can be used to measure prorenin. VTP-27999 is a new renin inhibitor with an aliskiren-like IC50 and t1/2, and a much higher bioavailability. This study addressed (pro)renin changes during treatment of volunteers with VTP-27999 or aliskiren. Both drugs increased renin immunoreactivity. Treatment of plasma samples from aliskiren-treated subjects with excess aliskiren yielded higher renin immunoreactivity levels, confirming the presence of prorenin. Unexpectedly, this approach did not work in VTP-27999-treated subjects, although an assay detecting the prosegment revealed that their blood still contained prorenin. Subsequent in vitro analysis showed that VTP-27999 increased renin immunoreactivity for a given amount of renin by ≥ 30% but did not unfold prorenin. Yet, it did bind to acid-activated, intact prorenin and then again increased immunoreactivity in a renin assay. However, no such increase in immunoreactivity was seen when measuring acid-activated prorenin bound to VTP-27999 with a prosegment-directed assay. The VTP-27999-induced rises in renin immunoreactivity could be competitively prevented by aliskiren, and antibody displacement studies revealed a higher affinity of the active site-directed antibodies in the presence of VTP-27999. In conclusion, VTP-27999 increases renin immunoreactivity in renin immunoassays because it affects the affinity of the active site-directed antibody. Combined with its lack of effect on prorenin, these data show that VTP-27999 differs from aliskiren. The clinical relevance of these results needs to be established.

Facilitated diffusion of angiotensin II from perivascular interstitium to AT1 receptors of the arteriole. A regulating step in vasoconstriction.

BACKGROUND: A kinetic model for the binding of angiotensin (Ang) II to AT1 receptors (AT1R) in arterioles in vivo did suggest a novel mechanism of stimulus amplification. OBJECTIVE: To further clarify the role of this mechanism in the functioning of the local renin-angiotensin systems, as opposed to circulating Ang II. METHODS AND RESULTS: The model was refined in order to account for geometric characteristics of the vascular smooth muscle (VSM) cells in arterioles with a single VSM cell layer. Results show that, unlike experiments in vitro, the graph of AT1R occupancy, that is, [Rec(occ)]/[Rec(total)] where [Rec(total)]=[Rec(occ)]+[Rec(free)], as a function of log [Ang II], is shifted to the left at higher [Rec(total)]. This leads to the concept of association rate amplification (ASRA) and facilitated Ang II diffusion. Considering that abluminal Ang II has to cross a diffusion fluid-barrier 1-10 times the glycocalyx to reach VSM AT1R, it appears that the ASRA factor is 1500 to 150 respectively, whereas more than 90% of Ang II is captured, at 10% occupancy, and with [Ang II] as low as 10(-15)-10(-14) mol/ml. Due to the presence of endothelium, intraluminal [Ang II] needs to be 20-30 times higher. ASRA favors a low [Ang II] threshold for AT1R stimulation, but it also favors a flat stimulus/response curve by promoting receptor-mediated endocytosis and receptor downregulation. CONCLUSION: The model predicts that, in small resistance vessels, abluminal rather than intraluminal Ang II is important for maintaining vasoconstrictor tone. ASRA minimizes the overflow of de-novo generated tissue Ang II into the circulation. It explains why Ang II acts at levels far below K(D), why AT1R blockers are effective in hypertension even when [Ang II] is low, and why the constrictor action of Ang II appears so much suppressed by sodium depletion.

Functional effects of renal artery stent placement on treated and contralateral kidneys.

BACKGROUND: This study examined the effects of stent placement for renal artery stenosis on the function of treated and contralateral kidneys. METHODS: Eighteen patients who underwent stent placement for unilateral renal artery stenosis presenting with hypertension and/or renal failure were studied before angiography and stent placement and at their one-year follow-up. Renal vein blood samples were taken at both sides, at each side simultaneously with a sample from the aorta, to measure the plasma renin concentration and the concentrations of 131I-hippuran and 125I-thalamate during constant systemic infusion of these radiochemicals. This allowed an assessment of the single-kidney contributions to the total renin secretion, effective renal plasma flow (131I-hippuran clearance) and glomerular filtration rate (125I-thalamate clearance). RESULTS: At the one-year follow-up, the vein-to-artery renin ratio at the treated side had decreased to normal, from 1.65 +/- 0.131 to 1.23 +/- 0.076 (mean +/- SEM; P = 0.011), indicating an improved renal blood flow. Contralaterally it rose from 1.09 +/- 0.042 to 1.17 +/- 0.029 (P = 0.055) at follow-up. The extraction ratio of 131I-hippuran improved at the treated side (0.48 +/- 0.049 to 0.62 +/- 0.034; P = 0.003) and contralaterally (0.67 +/- 0.033 to 0.73 +/- 0.026; P = 0.043). The extraction ratio of 125I-thalamate, which equals filtration fraction, improved at both sides (0.12 +/- 0.014 to 0.17 +/- 0.012 at the treated side, P = 0.001; 0.18 +/- 0.013 to 0.22 +/- 0.011 contralaterally, P = 0.002). Two-kidney effective renal blood flow and glomerular filtration rate remained unchanged. CONCLUSION: Renal artery stenting was capable of causing improvement of glomerular filtration rate of the treated kidney, although the overall glomerular filtration rate did not change.

Prorenin-induced myocyte proliferation: no role for intracellular angiotensin II.

Cardiomyocytes bind, internalize, and activate prorenin, the inactive precursor of renin, via a mannose 6-phosphate receptor (M6PR)--dependent mechanism. M6PRs couple directly to G-proteins. To investigate whether prorenin binding to cardiomyocytes elicits a response, and if so, whether this response depends on angiotensin (Ang) II, we incubated neonatal rat cardiomyocytes with 2 nmol/L prorenin and/or 150 nmol/L angiotensinogen, with or without 10 mmol/L M6P, 1 micromol/L eprosartan, or 1 micromol/L PD123319 to block M6P and AT(1) and AT(2) receptors, respectively. Protein and DNA synthesis were studied by quantifying [(3)H]-leucine and [(3)H]-thymidine incorporation. For comparison, studies with 100 nmol/L Ang II were also performed. Neither prorenin alone, nor angiotensinogen alone, affected protein or DNA synthesis. Prorenin plus angiotensinogen increased [(3)H]-leucine incorporation (+21 +/- 5%, mean +/- SEM, P<0.01), [(3)H]-thymidine incorporation (+29 +/- 6%, P<0.01), and total cellular protein (+14 +/- 3%, P<0.01), whereas Ang II increased DNA synthesis only (+34 +/- 7%, P<0.01). Eprosartan, but not PD123319 or M6P, blocked the effects of prorenin plus angiotensinogen as well as the effects of Ang II. Medium Ang II levels during prorenin and angiotensinogen incubation were <1 nmol/L. In conclusion, prorenin binding to M6PRs on cardiomyocytes per se does not result in enhanced protein or DNA synthesis. However, through Ang II generation, prorenin is capable of inducing myocyte hypertrophy and proliferation. Because this generation occurs independently of M6PRs, it most likely depends on the catalytic activity of intact prorenin in the medium (because of temporal prosegment unfolding) rather than its intracellular activation. Taken together, our results do not support the concept of Ang II generation in cardiomyocytes following intracellular prorenin activation.