enalaprilat-anhydrous and Cardiomegaly

The renin-angiotensin system (RAS) in the brain is involved in the pathogenesis of hypertension. We hypothesized that inhibition of angiotensin-converting enzyme (ACE) in the hypothalamic paraventricular nucleus (PVN) attenuates angiotensin II (ANG II)-induced hypertension via restoring neurotransmitters and cytokines. Rats underwent subcutaneous infusions of ANG II or saline and bilateral PVN infusions of ACE inhibitor enalaprilat (ENL, 2.5μg/h) or vehicle for 4weeks. ANG II infusion resulted in higher mean arterial pressure and cardiac hypertrophy as indicated by increased whole heart weight/body weight ratio, whole heart weight/tibia length ratio, left ventricular weight/tibia length ratio, and mRNA expressions of cardiac atrial natriuretic peptide and beta-myosin heavy chain. These ANG II-infused rats had higher PVN levels of glutamate, norepinephrine, tyrosine hydroxylase, pro-inflammatory cytokines (PICs) and the chemokine monocyte chemoattractant protein-1, and lower PVN levels of gamma-aminobutyric acid, interleukin (IL)-10 and the 67-kDa isoform of glutamate decarboxylase (GAD67), and higher plasma levels of PICs, norepinephrine and aldosterone, and lower plasma IL-10, and higher renal sympathetic nerve activity. However, PVN treatment with ENL attenuated these changes. PVN microinjection of ANG II induced increases in IL-1β and IL-6, and a decrease in IL-10 in the PVN, and pretreatment with angiotensin II type 1 receptor (AT1-R) antagonist losartan attenuated these changes. These findings suggest that ANG II infusion induces an imbalance between excitatory and inhibitory neurotransmitters and an imbalance between pro- and anti-inflammatory cytokines in the PVN, and PVN inhibition of the RAS restores neurotransmitters and cytokines in the PVN, thereby attenuating ANG II-induced hypertension and cardiac hypertrophy.

Topics: Angiotensin II; Animals; Cardiomegaly; Chemokine CCL2; Enalaprilat; gamma-Aminobutyric Acid; Glutamic Acid; Heart; Hypertension; Interleukin-10; Interleukin-1beta; Interleukin-6; Kidney; Losartan; Male; Neurotransmitter Agents; Norepinephrine; Organ Size; Paraventricular Hypothalamic Nucleus; Peptidyl-Dipeptidase A; Rats; Rats, Sprague-Dawley; Receptor, Angiotensin, Type 1; Renin-Angiotensin System

It has been known for a long time that systemic infusion of angiotensin II in patients with coronary artery disease or normal control subjects causes a marked increase in left ventricular end diastolic pressure (LVEDP) and systolic pressure (LVP) (1,2). In this setting angiotensin II produces a marked increase in afterload that makes it difficult to acknowledge possible local myocardial effects of the peptide. The studies (3-8) summarized in the present paper were designed to examine the physiological role of local cardiac angiotensin II generation and local bradykinin degradation on cardiac function in the normal and hypertrophied rat heart. Angiotensin I and angiotensin II, infused in isolated, well oxygenated, buffer perfused normal rat hearts, produced a mild increase in LVEDP with no change in systolic function (3). In contrast, in hypertrophied rat hearts, angiotensin I and angiotensin II caused a marked deterioration of diastolic function, increasing LVEDP from 10 to 25-37 mmHg on average (3,5). Preliminary evidence suggests that angiotensin II effects on diastolic function are mediated via a protein kinase C dependent pathway that might involve Na+/H+ exchange (4,5). When cardiac angiotensin converting enzyme was blocked by infusion of an ACE inhibitor prior and in parallel to angiotensin I infusion no changes in diastolic function were noted (6). Furthermore, ACE inhibition blunted the diastolic dysfunction during low flow ischemia in isolated hypertrophied rat hearts (7). This effect of ACE inhibition was even more remarkeable, since no exogenous angiotensin was infused in this experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Angiotensin I; Angiotensin II; Animals; Cardiomegaly; Diastole; Enalaprilat; Heart; In Vitro Techniques; Male; Myocardium; Peptidyl-Dipeptidase A; Rats; Rats, Wistar; Reference Values; RNA, Messenger; Ventricular Function, Left