Abstract-Cardiac hypertrophy is frequent in chronic hypertension. The renin-angiotensin system, via its effector angiotensin II (Ang II), regulates blood pressure and participates in sustaining hypertension. In addition, a growing body of evidence indicates that Ang II acts also as a growth factor. However, it is still a matter of debate whether the trophic effect of Ang II can trigger cardiac hypertrophy in the absence of elevated blood pressure. To address this question, transgenic mice overexpressing the rat angiotensinogen gene, specifically in the heart, were generated to increase the local activity of the renin-angiotensin system and therefore Ang II production. These mice develop myocardial hypertrophy without signs of fibrosis independently from the presence of hypertension, demonstrating that local Ang II production is important in mediating the hypertrophic response in vivo. (Hypertension. 1998;31:1324-1330.)

SUMMARY To measure specifically angiotensin-(l-8)octapeptide, peptides were extracted from 2 ml of plasma by reversible adsorption to bonded-phase silica. The angiotensin-(l-8)octapeptide was then isolated by isocratic reversed-phase high-performance liquid chromatography and quantified by radioimmunoassay. The extraction recovery of l25 I-angiotensin II added to 2 ml of plasma was 99 ± 2% (mean ± SD). The overall recovery of 5,10, and 20 fmol unlabeled angiotensin II added to 1 ml of plasma was 80 ± 10%. The coefficient of variation for within-assay precision was 0.06 and for between-assay precision 0.13. The detection limit was 0.4 fmol/ml. Buffer and plasma blanks were below the detection limit. Normal subjects on a free diet in supine position averaged 4.2 ± 1.7 fmol/ml angiotensin-(l-8)octapeptide. Furosemide (40 mg p.o.) and standing increased these values to 22 ± 7.6 fmol/ml. In four volunteers, immunoreactive "angiotensin II" (more or less angiotensinlike material) was measured serially before and after converting-enzyme inhibition (Hoe 498) with conventional Dowex extraction. At peak inhibition, plasma immunoreactive "angiotensin II" levels decreased by only 44%. In contrast, angiotensin-(l-8)-octapeptide isolated by high-performance liquid chromatography completely disappeared. In hypertensive patients receiving long-term treatment with enalapril, plasma levels ofangiotensin-(l-8)octapeptide fell from 2.7 ± 0.9 to0.9 ± 0.3 fmol/ml (mean ± SKM) 2 hours after the morning dose, whereas levels of immunoreactive "angiotensin II" were not significantly changed. We found that this sensitive method specifically measured angiotensin-(l-8)octapeptide and demonstrated that true angiotensin II virtually disappears during converting-enzyme inhibition.

SUMMARY Combining high-performance liquid chromatography with radioimmunoassay enabled the precise measurement of different angiotensins and their metabolites in plasma. Peptides were extracted from 2 ml of plasma by reversible adsorption to phenylsilyl-silica, separated by isocratic high-performance liquid chromatography, and quantitated by radioimmunoassay using a sensitive but suitably cross-reacting angiotensin II antiserum. For the C-terminal angiotensin II metabolites (2-8)heptapeptide, (3-8)hexapeptide, and (4-8)pentapeptide, overall recoveries of 10 fmol peptide added to 1 ml of plasma were (mean ± SD), 74 ± 6,68 ± 8, and 67 ± 11%, respectively. The detection limit for these peptides in plasma was 0.2 fmol/ml. Blanks were below the detection limits. In eight seated normal subjects treated for 4 days with enalapril, 20 mg p.o., q.d., angiotensin II metabolites tended to decrease during the 4 postdrug hours. However, their cumulated concentration in relation to octapeptide increased from 54 to 163% on Day 1 and from 62 to 103% on Day 4. After 4 hours of converting enzyme inhibition with enalapril there was still a close correlation between plasma renin activity and angiotensin-(l-8)octapeptlde level (r = 0.83, p<0.05) and between blood angiotensin I and angiotensin-(l-8)octapeptide levels (r = 0.86, p<0.01). Adding angiotensin I in vitro raised the angiotensin-(l-8)octapeptide levels after incubation at 4°C for 4 hours. Thus, immunoreactive "angiotensin II" does not disappear after converting enzyme inhibition largely because of the cumulated contribution of cross-reacting metabolites and partly because of in vitro generation of true angiotensin II. (Hypertension 8: 476-482, 1986) KEY WORDS • angiotensin I • angiotensin II • angiotensin III • angiotensin metabolites • peptide extraction • high-performance liquid chromatography • enalapril-induced converting enzyme inhibition • angiotensin antisera cross-reactivity • bonded-phase silica T HE beneficial effects of angiotensin (ANG) converting enzyme inhibitors in the treatment of hypertension and congestive heart failure are well established. Although these drugs were designed to block ANG II generation, immunoreactive "ANG II" (true ANG II plus cross-reacting material) does not disappear from the plasma with acute 1 "* or chronic 36 administration. Cross-reacting ANG I and other ANG peptides and metabolites are known to contribute to plasma immunoreactive "ANG II" and may explain its limited suppressibility during converting enzyme inhibition. Despite effective converting enzyme inhibition, other enzymes, such as tonin, 7 ' 8 chy-

No abstract