Richard N. Re

Tissue angiotensin system in cardiovascular medicine. A paradigm shift

16. Schwartz SM, Campbell GR, Campbell JH. Replications of smooth muscle cells in vascular diseases. Circ Res. 1986;58:427-444. 17. Gabbiani G, Kocher 0, Bloom WS, Vandekerckhova J, Weber K. Actin expression in smooth muscle cells of rat aortic intimal thickening, human atheromatous plaque, and cultured rat aorta media. J Clin Invest. 1984;73:148-152. 18. Morishita R, Gibbons GH, Ellison KE, Zhang L, Kaneda Y, Ogihara T, Dzau VJ. Autocrine/paracrine renin angiotension as a determinant of vascular structure: a gene transfer approach experiment. Hypertension. 1993;22:423. Abstract. 19. Paul M, Bachmann J, Ganten D. The tissue renin-angiotensin systems in cardiovascular disease. Trends Cardiovasc Med. 1992;2:

The role of the renin-angiotensin-aldosterone system in cardiovascular homeostasis in normal human subjects.

To examine the role of angiotensin II in the maintenance of blood pressure and the control of aldosterone secretion in man, eight normal subjects were studied on a tilt table in sodium replete and sodium depleted states prior to and subsequent to the intravenous infusion of an angiotensin converting enzyme inhibitor (CEI). In both the sodium replete or sodium depleted state, upright tilting resulted in an increase in heart rate and a narrowing of pulse pressure. None of the sodium replete or depleted subjects fainted. Tilting was accompanied by a rise in plasma renin activity with an associated rise in plasma aldosterone concentration. When converting enzyme inhibitor was administered, wbich blocked the generation of angiotensin II, sodium replete subjects were able to compensate for an upright tilt, despite the absence of angiotensin 11, without significant hemodynamic change when compared to control state. In sodium depleted subjects, after the administration of converting enzyme inhibitor, there was a sharp and significant decrease in systolic and diastolic blood pressure associated with a significant rise in heart rate. All but one sodium depleted subject fainted within seven minutes. Both plasma aldosterone concentration and plasma renin activity rose on tilting in both sodium replete and sodium depleted subjects. After the administration of converting enzyme inhibitor, plasma aldosterone failed to rise in association with a rise in plasma renin activity. In supine subjects, after the administration of converting enzyme inhibitor, plasma renin activity rose but plasma aldosterone concentration fell. In sodium depleted subjects, after the administration of CEI, aldosterone fell to a level significantly lower than that in supine controls and to a level no different from the supine sodium replete subject. These results indicate that angiotensin II is essential for blood pressure maintenance in sodium depleted individuals, that angiotensin II exerts a direct feedback control on renin secretion, and that angiotensin It is the primary stimulus to aldosterone secretion in response to both sodium depletion and to postur.

Renin synthesis by canine aortic smooth muscle cells in culture

Angiotensin-I generating activity has been detected in homogenates of arterial tissue but it remains unclear whether this enzymatic activity results from the presence of renin itself or from the action of other proteases such as cathepsin D. In an assay system employing anephric dog plasma as substrate and buffered to pH 7.4, we detected angiotensin-I generating activity in homogenates of canine aortic smooth muscle cells. This enzymatic activity was in large part inhibitable by renin-specific antisera raised to pure canine renal renin. Immunofluorescent study of cultured arterial smooth muscle cells was also performed using renin specific antiserum. Granular cytoplasmic immunofluorescence was detected when specific antirenin serum was used but not when preimmune serum was employed. The addition of pure canine renin to the renin antiserum during staining suppressed the granular immunofluorescence confirming the specificity of staining. Finally, biosynthetic radiolabelling studies were performed. Immunoprecipitation of newly synthesized proteins with antirenin serum and staphylococcal protein A followed by gel electrophoresis and autoradiography demonstrated the synthesis of an immunoreactive protein with the molecular weight of renin. Pretreatment of the antirenin serum with pure canine renin resulted in the disappearance of this immunoreactive protein band. Thus these studies provide multiple lines of evidence to indicate the in situ synthesis of renin by vascular smooth muscle cells.

Angiotensin II receptors in chromatin fragments generated by micrococcal nuclease.

Rat liver nuclei were digested with micrococcal nuclease following incubation with 125I-angiotensin II (AII) or with 125I-AII and excess unlabeled hormone. Chromatin enriched in 125I was solubilized after 3 min and was applied to a BIO-GEL A-5 M column. Labeled hormone was 40-60% displaceable by unlabeled hormone, in nucleoprotein eluting with a V/Vo near 1.9, indicating that these solubilized chromatin fragments contained specific receptors for AII. Furthermore, a discrete AII binding nucleoprotein particle was resolved on DNP gel electrophoresis. Additionally, binding to specific AII nuclear receptors appeared to bring about changes in chromatin structure consistent with the induction of transcriptional activity.

Inhibition of Angiotensin-Converting Enzyme for Diagnosis of Renal-Artery Stenosis

To determine its utility as an aid in diagnosis of renovascular hypertension, we administered nonapeptide converting-enzyme inhibitor (CEI) (which inhibits conversion of angiotensin I to angiotensin II) (0.25 mg per kilogram) to 14 unselected hypertensive patients undergoing bilateral renal-vein catheterization. In seven (Group I) predominantly unilateral disease was discovered by angiography (renal-artery stenosis in six and hydronephrosis in one); in the remaining seven (Group II) no rennal-artery abnormality was found. In Group I, mean (+/- S.E.) ratio of involved to uninvolved renal-vein plasma renin activity (PRA) increased from 2.94 +/- 0.91 before to 8.36 +/- 2.94 after CEI (P less than 0.01). In Group II, the ratio (of the initially higher to the lower side) was 1.99 +/- 0.49 before and 1.17 +/- 0.07 after CEI (P greater 0.02). Post-CEI PRA was predicted by pretreatment PRA. Mean blood pressure fell in both groups after CEI, and the decrement was predicted by pre-CEI PRA. These data suggest that CEI can be of use at the time of renal-vein catheterization, serving to increase diagnostic accuracy by increasing the difference in PRA between the two sides when there is unilateral disease.

The Nature of Intracrine Peptide Hormone Action

Current theory holds that peptide hormone action results from hormone binding to cell-surface receptors, with the generation of intracellular second messengers. However, a growing body of evidence suggests that intracellular peptide hormone, either internalized or synthesized in situ, can exert physiologically relevant effects. These effects are diverse and poorly understood. I propose that such intracrine action can serve to modulate cellular function over time and thereby play a role in biological memory of various sorts, in the maintenance of hormonal responsiveness, and in cellular differentiation.

The intracrine hypothesis: An update

The intracellular actions of peptide hormones, growth factors, as well as of extracellular-signaling enzymes and DNA-binding proteins, either within target cells or within their cells of synthesis has been called intracrine action. Although these intracrine moieties are structurally diverse, they share certain characteristics of synthesis and function. This has given rise to the development of a theory of intracrine action which permits testable predictions to be made regarding the functioning of these peptides/proteins. Here the intracrine hypothesis is briefly described and then recent experimental findings which bear on predictions made earlier on the basis of the theory are discussed. These findings provide new support for the intracrine hypothesis.

Effect of angiotensin II on RNA synthesis by isolated nuclei.

Peptide hormones are known to bind to cell surface receptors as the first step in the generation of their effects on target tissues. However, it remains uncertain whether internalized hormone might also play a role in the production of longterm or trophic effects of peptide hormones. Because the peptide hormone angiotensin II appears to be internalized by target cells, we studied the effect of this peptide on isolated hepatic nuclei. At both 5 X 10(-7)M and 5 X 10(-9)M, angiotensin II significantly increased RNA synthesis. This effect was not mimicked by Sar1-Ala8-angiotensin II (saralasin) or the unrelated nonapeptide teprotide.

Intracellular Renin and the Nature of Intracrine Enzymes

Recently, the binding of renin and prorenin to cellular receptors with the subsequent generation of second messengers and the production of physiological effects has been demonstrated. In addition, the internalization of prorenin by target cells has been associated with increased cellular synthesis of angiotensin and cardiac pathology. Also, a renin transcript lacking the sequences encoding a secretory signal has been reported, and this transcript appears to produce a renin that acts in the cell that synthesized it. Some years ago, we coined the term intracrine for a peptide hormone or factor that acts in the intracellular space either after internalization or retention in its cell of synthesis. Thus defined, a wide variety of peptides display intracrine functionality, including hormones, growth factors, transcription factors, and enzymes. For example, considerable evidence indicates that angiotensin II is an intracrine. Also, general principles of intracrine functionality have been developed. Thus, recent evidence demonstrates that the prorenin/renin molecule is an intracrine enzyme. Here, the actions of intracrine enzymes (angiogenin, phosphoglucose isomerase, phospholipase A2, granzyme A and B, thioredoxin, platelet-derived endothelial growth factor, and serine protease inhibitors) are reviewed. The relation of prorenin/renin to other intracrine enzymes, and to intracrines in general, is discussed.

Reliability of a Medication Adherence Measure in an Outpatient Setting

Background:Reliable approaches for measuring antihypertensive medication compliance in the outpatient setting are not readily available. The objective of the current study was to determine the reliability of the Hill-Bone Compliance Scale among elderly hypertensive patients. Methods:We conducted a cross-sectional survey of community-dwelling patients attending the hypertension section of the Internal Medicine Clinic in a large multispecialty group practice. Participants (n = 239) completed a self-administered questionnaire consisting of demographic questions and the Hill-Bone Compliance to High Blood Pressure Therapy Scale, which includes a nine-item medication compliance subscale. Results:The mean age of respondents was 69 years; 51% of patients were men, 73% were white, 86% had at least a high school education, and 61% were married. The Cronbach alpha was 0.68 for the medication compliance subscale. All nine items of the medication compliance subscale maintained higher correlations with their own subscale total than with the salt intake and appointment keeping subscale totals. After adjusting for other demographic variables, the odds ratio (95% confidence interval) of perfect medication compliance as reported on the medication compliance subscale was 1.71 (0.95–3.07) for participants 65 years of age and older versus those younger than 65 years of age, 2.53 (1.37–4.66) for whites versus nonwhites, 1.27 (0.73–2.20) for males versus females, 1.30 (0.73–2.29) for married versus unmarried participants, and 1.63 (0.74–3.62) for those with at least a high school education versus those with less education. Conclusion:The medication compliance subscale of the Hill-Bone Compliance Scale appears reliable and may be a useful tool for detecting noncompliant patients in outpatient settings.