Keiichi Ito

Effect of Angiotensin Converting Enzyme Inhibitor (Captopril) on Cerebral Blood Flow in Hypertensive Patients without a History of Stroke

The effect of the angiotensin converting enzyme inhibitor, captopril, on cerebral blood flow (CBF) was studied in 11 hypertensives without a history of stroke. Mean hemispheric CBF (mCBF) was measured in each patient by Xe-133 inhalation method before and after 7 days of captopril administration. Blood pressure (BP) both in the control state and at the time of CBF measurement decreased significantly after drug administration. mCBF, however, did not show any significant change. When percent changes in mCBF before and after the administration were plotted against those of mean arterial BP, significant inverse correlations were obtained in both hemispheres; the larger the BP decrease, the more increase in CBF was observed. It is concluded that captopril lowers systemic BP without concomitant decrease in CBF in hypertensive subjects with no history of stroke. Furthermore, the results suggest that captopril may have a vasodilating action on cerebral blood vessels.

The Existence of Inactive (Trypsin-Activated) Renin in Dog Plasma and Renin Granules from the Kidney

Trypsin-activated renin (inactive renin) was detected in the break-through fraction when dog plasma or renin extracted from renin granules (stored renin) was applied to a pepstatin column, respectively. The appearance of the renin activity by trypsin treatment was not due to acid protease. Production of angiotensin I from homologous renin substrate by the trypsin-activated renin was proportional to the time of incubation. The trypsin-activated renin had an affinity for the pepstatin column. The maximum amount of trypsin-activated renin was obtained with incubation for 15 min at 37 degrees C at 1000 micrograms/ml in plasma or at 100 micrograms/ml in case of stored renin. The ratio of inactive to active renin was calculated to be 1.6 or 0.002 in plasma or stored renin, respectively, under conditions of a standard sodium diet.

ALPHA-FORM OF ATRIAL NATRIURETIC PEPTIDE RELEASED FROM DOG ATRIUM DURING ATRIAL DISTENSION

To assess the released form of atrial natriuretic peptide (ANP) during atrial distension, we compared the form of ANP before and during atrial distension in anesthetized dogs, using radioimmunoassay combined with high performance liquid chromatography (HPLC). When increasing the left atrial pressure (LAP) from 2.2 +/- 0.9 mmHg to 9.4 +/- 1.3 mmHg, the plasma ANP concentration in the coronary sinus was increased by 190% over the control, during left atrial distension. The major form of the released ANP extracted in the blood sample obtained from the coronary sinus was alpha-form. However other unidentified immunoreactive peaks, preceding and following the main peak were also discernible. These results suggest that the major form of ANP released during left atrial distension was the alpha-form.

Risk Factor of Cerebral Arteriosclerosis Studied by Cerebral Angiography

1969年より1974年の5年間に種々の愁訴にて脳血管撮影を施行されながら, 動脈硬化以外の器質的病変を指摘できなかった315例を対象に年齢・血圧・血清総コレステロール値と脳動脈硬化所見との関連を検討した. 脳動脈硬化所見は頚動脈撮影にて造影される動脈系を頭蓋外頚動脈・頭蓋内主幹動脈・頭蓋内小動脈の3部位に区分し, 狭窄及び管径不同の有無・範囲により動脈硬化の程度を3段階に分けた.1) 頭蓋外頚動脈・頭蓋内主幹動脈・頭蓋内小動脈の各部位で, 当然ながら年齢は動脈硬化の主たる危険因子であることが認められた. 又, 頭蓋内主幹動脈は他の動脈系に比較し, 動脈硬化所見を指摘できる頻度が高く, 動脈硬化の好発部位と考えられた.2) 各動脈系とも高血圧群で動脈硬化がより進行しているといえたが, 年齢別検討で推計学上有意差が得られたのは頭蓋内小動脈との関連を50歳台及び60歳台についてみた場合のみで, 高血圧は特に管径の小さな動脈系の硬化との関連が認められた.3) 高血圧群では血清総コレステロール値の上昇と共に, 頭蓋外頚動脈及び頭蓋内主幹動脈硬化例の頻度は高くなった. 特に頭蓋内主幹動脈の硬化とコレステロール値の関連性は5%の危険率で有意であった. コレステロール値が210mg/dl以上の高血圧例では症例の26.5%が頭蓋内主幹動脈に25%以上の狭窄を合併しており,184mg/dl以下の例に比較し約5倍の頻度に達した. 非高血圧群ではコレステロール値と動脈硬化度との間に明らかな関連を見出すことはできなかった.