Isamu Miyamori

Vascular aldosterone. Biosynthesis and a link to angiotensin II-induced hypertrophy of vascular smooth muscle cells.

Mineralocorticoids have been suggested to act on blood vessels, leading to increased vasoreactivity and peripheral resistance. However, the site of their production has so far been believed to be only the adrenal cortex. Here, we show direct evidence that vascular cells per se are aldosteronogenic, possessing their own system that responds to the steroid. Using polymerase chain reaction after reverse transcription, the CYP11B2 mRNA encoding the key enzyme for the biosynthesis of aldosterone was detected in both endothelial cells and smooth muscle cells cultivated from human pulmonary artery. The aldosterone receptor (type 1 mineralocorticoid receptor) gene was also found to be expressed in smooth muscle cells and, to a lesser extent, in endothelial cells. CYP11B2 gene expression in smooth muscle cells was stimulated by angiotensin II, the effector peptide of the renin-angiotensin system. Furthermore, the angiotensin II-induced increase in [3H]leucine incorporation in smooth muscle cells was significantly enhanced by aldosterone but inhibited by ZK 91587, a type 1 mineralocorticoid receptor antagonist. This may indicate that vascular aldosterone participates in the angiotensin II-induced hypertrophy of vascular smooth muscle cells. The present study therefore provides the starting point for a novel understanding of the molecular basis of vascular remodeling and hypertension.

Production of Aldosterone in Isolated Rat Blood Vessels

Angiotensin I (Ang I), Ang II, angiotensinogen, and renin are formed locally in the vasculature. We undertook this study to determine whether the rat mesenteric artery produces aldosterone and to investigate the effects of adrenalectomy, an angiotensin-converting enzyme inhibitor, Ang II, or potassium on aldosterone production in vascular tissue. Isolated rat mesenteric arteries were perfused with Krebs-Ringer solution for 4 hours. The perfusate was collected and chromatographed in a reversed-phase high-performance liquid chromatographic (HPLC) system. The fraction corresponding to synthetic aldosterone was collected and analyzed by mass spectrometry. The aldosterone concentration in the perfusate from the adrenalectomized rats and rats treated with an angiotensin-converting enzyme inhibitor was measured using radioimmunoassay after HPLC separation. The mass spectra of synthetic aldosterone and aldosterone isolated from the perfusate of rat mesenteric arteries were identical. Aldosterone production in the mesenteric arteries of adrenalectomized rats was increased and of rats treated with an angiotensin-converting enzyme inhibitor was reduced compared with that of controls. Ang II (1.9 x 10(10) mol/L) and potassium (6.0 mmol/L) increased aldosterone production in mesenteric arteries. This study shows that the rat mesenteric artery produces aldosterone and that the intravascular renin-angiotensin-aldosterone system may contribute to vascular tone.

Aldosterone biosynthesis and action in vascular cells

In view of the hypothetical possibility that the vascular renin-angiotensin system (RAS) might include aldosterone biosynthesis and action in the vasculature, we have undertaken a study to identify aldosterone released into the perfusion circuit from the rat mesenteric artery, and to investigate the effects of an angiotensin converting enzyme inhibition (ACEI) on aldosterone production from the vasculature. After 30 min equilibration, 240 mL of perfusate was collected and subjected to reverse-phase HPLC and subsequent mass spectrometry. Mass spectra corresponding to authentic corticosterone and aldosterone were obtained from the samples of mesenteric artery perfusate. Production of aldosterone in the mesenteric artery was not changed by adrenalectomy, although it was reduced in the arterial perfusate from rats pretreated with ACEI. By RT-PCR the expression of CYP 11B2 and mineralocorticoid receptor genes were demonstrated in both vascular endothelial and smooth muscle cells. These studies constitute indirect evidence supporting our hypothesis that locally produced aldosterone in the vascular tissue acts on vascular tone and remodeling via a paracrine or autocrine manner.

The expression of steroidogenic enzyme genes in human vascular cells

Recently, we demonstrated that aldosterone is produced by human vascular cells, and that vascular aldosterone is linked to angiotensin II‐induced hypertrophy of vascular smooth muscle cells. We therefore examined whether genes encoding steroidogenic enzymes responsible for aldosterone biosynthesis from cholesterol are expressed in vascular cells. Using polymerase chain reaction after reverse transcription, type I and II 3β‐HSD (3β‐hydroxysteroid dehydrogenase), P‐450c21 (21‐hydroxylase), and P‐450c18 (18‐hydroxylase/oxidase) genes were found to be expressed both in endothelial cells and smooth muscle cells cultivated from human pulmonary arteries. However, P‐450scc (cholesterol side chain cleavage enzyme) and P‐45011β (11β‐hydroxylase) mRNAs could not be detected. These findings suggest that the enzyme system responsible for aldosterone production in human vascular cells is different from that found in the adrenal cortex and that vascular aldosterone may be synthesized from metabolic intermediates which originate from the circulation. Extra‐adrenal 3β‐HSD and steroid 21‐hydroxylase occur in a wide variety of tissues. Thus, human vascular cells can retain the ability to produce aldosterone by expressing the P‐450c 180 gene.

Malignant pheochromocytoma with features suggesting the brown-séquard syndrome. A case report

A case of malignant pheochromocytoma arising from the abdominal preaortic chromaffin tissue is presented. Of particular note is that right hemiplegia associated with sensory disturbances, compatible with the Brown‐Séquard syndrome, was an outstanding early clinical manifestation. The patient finally developed signs of complete transection of the spinal cord which was caused by metastasis of the tumor to the cervical spines. The neurological abnormalities observed in the present case were so unusual in pheochromocytoma as to lead initially a diagnosis of cord tumor. Autopsy findings well supported the clinical diagnosis. Cases like this have not been reported so far. Cancer 40:402–405, 1977.

A crossover comparison of urinary albumin excretion as a new surrogate marker for cardiovascular disease among 4 types of calcium channel blockers

BACKGROUNDnAt the intervention for cardiovascular disease (CVD), albuminuria is a new pivotal target. Calcium channel blocker (CCB) is one of the most expected agents. Currently CCBs have been classified by delivery system, half-life and channel types. We tested anti-albuminuric effect among 4 types of CCBs.nnnMETHODSnSubjects were 50 hypertensives (SBP/DBP 164.7±17.1/92.3±12.2mmHg, s-Cr 0.81±0.37mg/dl, urinary albumin excretion (UAE) 69.4 (33.5-142.6) mg/gCr). Four CCBs were administered in a crossover setting: nifedipine CR, a long biological half-life L type by controlled release; cilnidipine, an N/L type; efonidipine, a T/L type; and amlodipine, a long biological half-life L type.nnnRESULTSnComparable BP reductions were obtained. UAE at endpoints ware as follows (mg/gCr, *P<0.01): nifedipine CR 30.8 (17.3-81.1),* cilnidipine 33.9 (18.0-67.7),* efonidipine 51.0 (21.2-129.8), amlodipine 40.6 (18.7-94.7). By all agents, significant augmentations were observed in PRA, angiotensin I and angiotensin II (AngII). AngII at cilnidipine was significantly lower than that at amlodipine. PAC at cilnidipine and efonidipine was significantly lower than that at amlodipine. Nifedipine CR significantly reduced ANP concentration.nnnCONCLUSIONSnIt is revealed that only nifedipine CR and cilnidipine could reduce albuminuria statistically. Thus, it is suggested that the 2 CCBs might be favorable for organ protection in hypertensives.

Biosynthetic pathway of 19-noraldosterone in isolated rat glomerulosa cells

The biosynthetic pathway of 19-noraldosterone (19-noraldo) in isolated rat glomerulosa cells (GC) and fasciculata-reticular cells (FC) was studied by analyzing [14C]pregnenolone metabolism using HPLC and quantification by specific RIA. In GCs, 18,19-dihydroxycorticosterone was detected after 15 min incubation with [14C]pregnenolone, 18-hydroxy-19-norcorticosterone was detected after 30 min and 19-noraldo was detected after 45 min before the appearance of an aldosterone peak. These three mineralocorticoids were not detected in FCs. The results demonstrate that 19-noraldo is synthesized in GCs and then undergoes further metabolism.