1. The effects of renin inhibitor ES-8891 on renin synthesis and its secretion by the kidney were investigated in normotensive sodium-depleted marmosets. We measured plasma renin activity, plasma immunoreactive renin concentration, plasma angiotensin II concentration and kidney renin mRNA content after oral administration of ES-8891 (60 mg day−1 kg−1) for 1 week.
2. The mean blood pressure was significantly decreased (P< 0.01) on day 7 after oral administration of ES-8891. There was no significant change in heart rate during the administration.
3. Oral administration of ES-8891 for 1 week markedly decreased the plasma renin activity, the plasma immunoreactive renin concentration and the plasma angiotensin II concentration (to 18%, 41% and 24% of the corresponding control values; P < 0.05 for each, n = 5).
4. The kidney renin mRNA content in ES-8891-treated marmosets was significantly lower than that in normal controls (4.2 ± 3.5 versus 12.8 ± 5.5 pg/μg of total RNA, means ± sd, P < 0.05, n = 5).
5. Oral administration of the renin inhibitor ES-8891 for 1 week not only inhibited plasma renin activity but also decreased renin synthesis and its secretion by the kidney.