In acute experiments, we demonstrated previously that nitric oxide (NO) donors exogenously applied to the nucleus tractus solitarii (NTS) depressed the baroreceptor cardiac reflex. In this study, we determined a role for endogenous endothelial nitric oxide synthase (eNOS) activity in the NTS for chronically regulating baroreceptor reflex function in conscious rats. A recombinant adenoviral vector directing expression of a truncated form of eNOS was microinjected bilaterally into the NTS to inhibit endogenous eNOS activity. Arterial pressure was monitored continuously using radio-telemetry in freely moving animals and spontaneous baroreceptor reflex gain (sBRG) determined by a time-series method. sBRG showed a gradual increase from day 7 to 21 after gene transfer and the value at day 21 (1.68 ± 0.20 ms mmHg _1 , n = 6) was significantly higher than that before gene transfer (1.13 ± 0.09 ms mmHg _1 , P < 0.001). This value was also significantly higher than that in rats in which enhanced green fluorescent protein (eGFP) was expressed in the NTS (1.04 ± 0.21 ms mmHg _1; n = 6, P < 0.01) and saline-treated groups (1.12 ± 0.15 ms mmHg _1 ; n = 4, P < 0.05), which did not change from control levels. In addition, heart rate decreased from 336 ± 6 to 318 ± 8 b.p.m. (P < 0.05) 21 days after gene transfer. This value was also significantly lower than that in control groups (eGFP: 348 ± 9 b.p.m., n = 6, P < 0.01; saline: 347 ± 5 b.p.m., n = 4, P < 0.05). Gene transfer did not affect arterial pressure. These findings suggest that in the conscious rat eNOS is constitutively active within the NTS and is a factor regulating baroreceptor reflex gain and heart rate.

The blood pressure of spontaneously hypertensive rats (SHRs) decreased after oral administration of an extract prepared from chicken breast muscle, falling maximally to 50 mmHg lower than before. This effect continued for at least 4 h after administration. The peptides possessing hypotensive activity in the chicken extract were examined by measuring the inhibitory activity (IC(50)) against angiotensin I-converting enzyme (ACE). The inhibitory activity of the chicken extract was 1060 mg%, whereas the activity of the extract treated with an Aspergillus protease and gastric proteases (trypsin, chymotrypsin, and intestinal juice) became stronger, reaching 1.1 mg%. Peptides in this hydrolysate of the extract were isolated by HPLC on a reversed-phase column, and their N-terminal sequences were analyzed. Three peptides possessed a common sequence, Gly-X-X-Gly-X-X-Gly-X-X, which was homologous with that of collagen. The peptide Gly-Phe-Hyp-Gly-Thr-Hyp-Gly-Leu-Hyp-Gly-Phe showed the strongest inhibitory activity (IC(50) = 42 microM).

Water is essential to life processes and has a number of significant functions. The ingredients of drinking water as well as nutrients in foodstuffs are now considered important to people's health. Deep-sea water in particular has started to receive attention for its rich inorganic nutrients such as Mg, Ca, and K 1,2) which are due mainly to less photosynthesis of plant plankton and much organic decomposition. In addition to the beneficial effects of these minerals on the cardiovascular system, unknown effects of some ultratrace elements or unknown substances in deep-sea water may be found in future. Some scientific evidences of therapeutic or preventive effects of deep-sea water have been reported recently. Deepsea water improved mineral imbalances and atopic eczema/ dermatitis syndrome in humans 2) and was effective in the prevention of hyperlipidemia and atherosclerosis in cholesterol-fed rabbits. 3,4) We expect that the continuous intake of deep-sea water could prevent hypertension as well as hypercholesterolemia, because investigators have revealed that oral supplementation of calcium 5,6) or magnesium 7,8) to hypertensive patients lowered blood pressure in addition to reducing the serum total cholesterol level. 7)Hypercholesterolemia and hypertension occur due to genetic as well as dietary factors. The Kurosawa and KusanagiHypercholesterolemic (KHC) rabbit is an animal model of spontaneous hypercholesterolemia (Type IIa) and atherosclerosis established by inbreeding a mutant of the Japanese White rabbit discovered by Japan Laboratory Animals, Inc. in 1985.9) The KHC rabbit is deficient in LDL-receptors in the liver and shows an abnormally increased LDL-cholesterol level without unusual deposits of fat in some organs.9) Atherosclerosis develops in the aortic arch and around bifurcations of the main branch arteries by the age of 3 months.9) We also reported previously that young adult KHC rabbits aged 10-12 months showed mild hypertension compared to agematched normal rabbits in addition to hypercholesterolemia, though atherosclerotic lesions were relatively in the earlystage. 10,11) The mild hypertension is thought to be independent of hypercholesterolemia.11) Intervention of either hypercholesterolemia or hypertension is considered to be inadequate to prevent progression of atherosclerosis and related cardiovascular events if hypertension and hypercholesterolemia coexist.12) Ca and Mg in deep-sea water could suppress absorption of cholesterol in the small intestine in cholesterol-fed rabbits, which might contribute to anti-hypercholesterolemic action of deep-sea water.3,4) Therefore, it is appropriate to use spontaneous hypercholesterolemic rabbits.In the present study, we investigated the effect of the intake of refined deep-sea water at a degree of hardness of 1000 for 6 months on hypercholesterolemia and mild hypertension in KHC rabbits aged 4 months, at which time atherosclerosis starts to occur in the ascending aorta and around orifices of branch arteries, by measuring serum and plasma biochemical par...

_1, P < 0.001) while sBRS was significantly decreased (0.53 ± 0.03 vs. 1.08 ± 0.08 ms mmHg _1 , P < 0.001). In sino-aortic denervated rats the change in SBP in response to dynamic exercise was significantly larger than that in baroreceptor-intact rats (denervated: 21.6 ± 2.5 mmHg; intact: 12.0 ± 2.8 mmHg, P < 0.05). In contrast, denervation made no difference to the change in HR. Although disabling eNOS activity in the NTS by adenoviral-directed expression of a dominant negative mutant form of eNOS increased resting sBRS (1.48 ± 0.20 vs. 1.09 ± 0.15 ms mmHg _1 , P < 0.05), the absolute level reached during dynamic exercise was identical to control. These results demonstrate that during dynamic exercise (i) the sBRS decreases around the operating point of the baroreceptor-cardiac reflex function curve in normotensive rats, (ii) the baroreceptor reflex operates to limit the rise in arterial pressure, and (iii) the attenuation of sBRS is not mediated by changes in eNOS activity within the NTS. Experimental Physiology (2003) 88.4, 517-526. 2545