Converting enzyme, angiotensin II and hypertensive disease

Angiotensin I converting enzyme activity in hypertension. Relationship to blood pressure, renin-sodium profiles, and antihypertensive therapy

The activity of the angiotensin I converting enzyme was measured in 55 patients with untreated essential hypertension, 11 patients with untreated renovascular hypertension, five patients with untreated primary aldosteronism, and 23 normotensive subjects. Converting enzyme activity was significantly higher (p less than 0.025 or less) in essential hypertension (28 +/- 1 units/ml) and renovascular hypertension (28.5 +/- 3 units/ml) when compared with the activity in the normotensive subjects (21 +/- 1.5 units/ml). Seventeen (31 percent) of the patients with essential hypertension and three (27 percent) patients with renovascular hypertension had an elevated converting enzyme activity above the mean +2 standard deviations value of the normotensive subjects (32.8 units/ml), ranging from 33 to 55.8 units/ml. Converting enzyme activity was similar in black and white patients and in male and female patients, but it tended to decrease with increasing age in both the hypertensive and the normotensive subjects. In the untreated patients with essential hypertension (n = 55), converting enzyme activity was inversely related to mean arterial pressure and age (r = -0.34, p less than 0.01) and positively related to plasma renin activity (r = 0.31, p less than 0.05). Converting enzyme activity was always decreased during captopril therapy, and it was not affected by beta blockers, but it was increased by diuretics. These findings indicate that converting enzyme activity is elevated in patients with essential and renovascular hypertension.

Comparison of serum angiotensin-converting enzyme in Graves' disease, toxic nodular goiter, and other thyroid conditions

Angiotensin-converting enzyme (ACE) was measured in plasma of patients with Graves' disease and with toxic nodular goiter, as well as in their treated counterparts and in normal controls. A significant elevation of ACE levels and a positive correlation between ACE, thyroxine, and triiodothyronine levels was found in both groups of thyrotoxicosis. Parallel fluctuations of triiodothyronine and ACE levels, albeit with a certain lag of the latter, was observed in patients in whom multiple measurements were taken. ACE levels, which were also determined in hypothyroid patients and in patients with euthyroid goiter on suppression therapy, were in the same range as normal controls and as in treated thyrotoxic patients. We conclude that the pathogenesis of thyrotoxicosis does not play a role in ACE elevation but that increased thyroid hormone seems to induce elevation of ACE. ACE elevation in thyrotoxicosis may constitute an integral part of the renin-angiotensin axis.

Polymyalgia rheumatica and giant cell arteritis--rational diagnosis and treatment predicated and disordered prostaglandin metabolism

We suggest that polymyalgia rheumatica with giant cell arteritis (PR-GCA) is an arachidonic acid metabolites mediated disease which can be diagnosed more accurately and monitored more precisely for therapeutic benefits by the serial determinations of the major urinary prostaglandin F, serum urinary lysozymes, serum acid phosphatase, and serum angiotensin converting enzyme rather than by the erythrocyte sedimentation rate, and, when necessary by temporal artery biopsy. The pathogenetic role proposed for prostaglandins (PG) and, even more precisely perhaps, the leukotrienes in this disease is consistent with the several published clinical observations that non-steroidal anti-inflammatory drug treatment produces in some cases a therapeutic paradox of symptomatic relief with concurrent, if clinically silent, progression of the arteritis, even to blindness. Furthermore, the impressive response of PR-GCA to low maintenance dose steroid therapy, a clinical conundrum for decades, is rationally explained on the basis of depressed or obstructed PG metabolism early on in the metabolic cascade. These views warrant clinical evaluation, confirmation or correction in whole or in part, and may increase our understanding of PR-GCA.

Effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation in man

The effects of the converting enzyme inhibitor (SQ 20881) on the pulmonary circulation were investigated in 13 patients in whom systemic hypertension developed following coronary artery bypass surgery. Pulmonary vascular resistance was decreased by the inhibitor, from 128 +/¿ 19 to 92 +/- 20 dynes sec cm-5 (or by 30 +/- 7 per cent; P less than 0.005), and this resulted in a decrease in mean pulmonary artery pressure from 17 +/- 1 to 13 +/- 1 mm Hg (or by 23 +/- 3 per cent, P less than 0.005). Consequently, right ventricular work was decreased by the inhibitor by 30 per cent (P less than 0.01), despite an increase in cardiac output (increase in stroke volume) by 16 +/- 6 per cent (P less than 01). This increase occurred despite a 13 +/- 3 per cent decrease in right ventricular filling pressure. The changes in pulmonary vascular resistance correlated with the pretreatment plasma renin activity (r = 0.74, P less than 0.01), as did the decrease in mean pulmonary artery pressure (R = 0.82, P less than 0.001), but neither change was related to the decrease in left ventricular fillling pressure nor to changes in cardiac output or mean arterial pressure. These results indicate that blockade of the formation of angiotensin II by the converting enzyme inhibitor results in reductions in pulmonary vascular resistance and pulmonary artery pressure which are unrelated to alterations in left ventricular function. Thus, angiotensin inhibition may have therapeutic value in various clinical states characterized by pulmonary hypertension--especially if renin levels are high.