Keiichi Iwanaga

Effect of Age on Active and Inactive Plasma Renin in Normal Subjects and in Patients with Essential Hypertension

The effect of age on the levels of active and trypsin‐activatable inactive plasma renin was examined in 41 normal subjects and 54 patients with essential hypertension, during recumbency and after stimulation with furosemide and ambulation. Active renin levels in supine subjects and patients decreased with age. Inactive renin levels did not change with age in normal subjects, whereas in hypertensive patients they decreased with age. Following stimulation with furosemide and ambulation, the levels of active renin increased but the responsiveness to stimulus decreased with age in both groups. In contrast, inactive renin levels slightly increased after furosemide administration and ambulation, resulting in an increased proportion of active to total renin. These data show that an acute stimulation with furosemide and ambulation affects mainly the active form of plasma renin, and the effect of age on inactive plasma renin in normal subjects may be different from that in patients with essential hypertension.

Long‐term effects of captopril in hypertension

Captopril was given for treatment of hypertension alone or in combination with diuretics to 32 patients for 1‐ to 4‐mo periods. The decrement of mean blood pressure after 1 and 2 mo correlated with pretreatment plasma renin activity (PRA) and the response of blood pressure to infusion of an angiotensin II antagonist. These correlations were no longer apparent after 4 mo of treatment. When subjects with a decrement of mean blood pressure that exceeded 13 mm Hg were compared with nonresponders, responders not only had higher control PRA and higher PRA at 1 mo of treatment, but also had decreased plasma aldosterone levels, decreased urinary aldosterone excretion, and increased serum postassium levels that persisted over the 4 mo of observation. The reduction of plasma aldosterone correlated with the fall of mean blood pressure. Urinary kallikrein, catecholamines, electrolytes, and endogenous creatinine clearance did not change in response to treatment. These findings indicate that the antihypertensive activity of captopril on long‐term administration probably depends in part on the blockade of angiotensin II, but other mechanisms cannot be excluded.

Urinary Catecholamine Response to Glucagon in Young and Elderly Patients with Essential Hypertension

本態性高血圧症, 血圧維持機構における交感神経系の関与が注目されている. しかし, 多種の要因が複雑に関与しているため現在のところ明確な結論は得られていない. 今回, 本態性高血圧症における加齢による交感神経系の関与の差異を検索するため, グルカゴン負荷時の尿中カテコールアミン反応性 (尿中アドレナリンおよびノルアドレナリン排泄値) を指標とすることにより, 老年性および若年性本態性高血圧症の交感神経系機能を比較検討した. その結果, 1) 若年性本態性高血圧症患者において, 交感神経系の反応性亢進をみたが, 2) 老年性本態性高血圧症患者においては, 交感神経系の反応性亢進は認められなかった. また, 3) 若年性および老年性の正血圧者群においては, 交感神経系反応性に有意な差異が認められず, 今回の実験に関する限り, 正血圧者群における加齢による交感神経系の反応性変化は認められなかった. 以上の結果より, 本態性高血圧症における病因としての交感神経系の関与は, 若年性本態性高血圧症では強く疑われたが, 老年性本態性高血圧症においては認める事ができなかった.

[Comparison of blood pressure responses to captopril, an orally active converting enzyme inhibitor, in rats with various forms of experimental hypertension (author's transl)].

Captopril, a potent and orally active converting enzyme inhibitor is believed to exert its hypotensive effect largely through the inhibition of the renin-angiotensin system (RAS) . In order to examine the renin dependency of blood pressure (BP) in normal rats and rats with two-kidney Goldblatt hypertension (2KGH), spontaneous hypertension (SH) and DOCA-salt hypertension (DSH), we examined the responses of these animals to prolonged administration of captopril. Two types of studies were done on the hypertensive animals: one was performed in the chronic phase when hypertension was established (chronic phase study), and the other was started in the prehypertensive phase (prevention study). Normal rats were studied with and without captopril treatment. 2KGH rats and SHR in the chronic