We evaluated the effects of long-term treatment with benidipine, a long-acting calcium antagonist, on endothelial cell-type nitric oxide synthase (eNOS) activity and eNOS mRNA expression in the left ventricle (LV) and its relation to coronary flow reserve, and microvascular remodeling in renovascular hypertensive rats (RHR: 2K-1C Goldblatt). Benidipine (5 mg/kg/day) was given to RHR (B-RHR, n = 11) for 6 weeks. Vehicle-treated RHR (U-RHR, n = 11) and age-matched sham-operated rats (ShC, n = 11) served as control group. Coronary flow reserve was measured in conscious rats using colored microspheres. Fifty-micrometer slices of the LV were incubated with L-arginine to measure nitrite production using the Griess method and eNOS mRNA expression was determined by reverse transcription-polymerase chain reaction. An increased blood pressure in RHR was significantly decreased by benidipine. Nitrite production and eNOS mRNA expression in the LV of U-RHR was significantly lower than that of ShC. This suppression of nitrite production and eNOS mRNA expression was significantly reversed in B-RHR. U-RHR demonstrated a significant decrease in coronary flow reserve and capillary density, and a significant increase in wall-to-lumen ratio, perivascular fibrosis, myocardial fibrosis, and myocyte cross-sectional area. These impaired factors were improved significantly by benidipine. These findings suggest that benidipine therapy may increase nitrite production and eNOS mRNA expression not only by lessening the endothelial damage by the reduction of blood pressure levels, but also by the stimulation of NOS activity and eNOS mRNA, and this increased NOS activity and eNOS mRNA expression may play a role in the amelioration of coronary flow reserve and microvascular remodeling.

Subdepressor dose of imidapril may ameliorate the endothelial damage not only by inhibiting production of angiotensin II but also by promoting eNOS and inhibiting iNOS mRNA and protein expression in the LV, and this increased eNOS mRNA and protein level may have a role in the improvement of congestive heart failure and myocardial remodelling.

Cilnidipine is a new and unique 1,4-dihydropyridine calcium antagonist that has both L-type and N-type voltage-dependent calcium channel blocking actions. We compared the effects of cilnidipine and another once-daily dihydropyridine calcium antagonist, nisoldipine, on 24-h blood pressure and heart rate in patients with essential hypertension.We enrolled 10 hypertensive outpatients [9 men and 1 woman; age, 55 + 3 yr (means ± SEM)] in this study. Their ambulatory blood pressure and heart rate were monitored for 24 h at intervals of 30 min with a portable recorder (TM-2425) after 8 wk of treatment with cilnidipine (5 to 20 mg once daily) and after 8 wk of treatment with nisoldipine (5 to 20 mg once daily). The order of the two treatments was randomized. Blood pressure and heart rate measurements for a 24-h period were analyzed for four segments of the day: morning (06:00 to 11:30), afternoon (12:00 to 17:30), nighttime (18:00 to 23:30), and sleeping time (0:00 to 5:30). Blood pressure levels were similar during the two treatment periods for each 6-h segment of the day. Heart rate was significantly higher during treatment with nisoldipine than during treatment with cilnidipine in the morning segment [by 4.1 ± 1.3 beats/mmn (p < 0.05)] and the afternoon segment [by 6.4 ± 3.6 beats/mmn (p < 0.05)]. These results suggest that cilnidipine is effective as a once-daily antihypertensive agent and causes reflex tachycardia less than does nisoldipine. (Hypertens Res 1998; 21: 215-219)

Chronically administered N(omega)nitro-L-arginine methyl ester (L-NAME) produces vascular structural changes and fibrosis of the left ventricle (LV). However, very few studies have evaluated whether the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors on these myocardial remodelings are associated with local gene expression of nitric oxide synthase (NOS) and ACE mRNA in the LV. Effects of long term treatment with imidapril, an ACE inhibitor, on gene expression of endothelial-cell NOS (eNOS) and ACE mRNA in the LV and its relation to myocardial remodeling in L-NAME-induced hypertensive rats were evaluated. Fifteen male Sprague-Dawley rats were given L-NAME (60 mg/ kg/day) in drinking water for 6 weeks to induce hypertension, and then treated with imidapril (L-NAME-I, n = 8, 1 mg/kg/day, subdepressor dose), or a vehicle (L-NAME-V, n = 7) for 4 weeks. Age-matched rats (C, n = 7) served as a control group. Blood pressure in L-NAME-V and L-NAME-I was similar and significantly higher than that in C. The level of eNOS mRNA in the LV was significantly decreased in L-NAME-V compared with C, and was significantly increased in L-NAME-I compared with C and L-NAME-V. The ACE mRNA and type I collagen mRNA expression levels were significantly increased in L-NAME-V compared with C, and significantly suppressed in L-NAME-I compared with L-NAME-V. L-NAME-V demonstrated a significant increase in wall-to-lumen ratio, perivascular fibrosis, and myocardial fibrosis. These changes in the microvasculature were improved significantly by imidapril. Myocardial remodeling in L-NAME-induced hypertensive rats was significantly ameliorated by a subdepressor dose of imidapril, which may be due to an increase in local eNOS mRNA expression and a decrease in angiotensin II in the LV.

In the heart, nitric oxide activates an adenosine triphosphate (ATP)-sensitive K (K(ATP)) channel that is constructed of two subunits, i.e., an ATP-binding cassette protein sulfonylurea receptor (SUR2) and a pore-forming inward rectifier (Kir6.1 or 6.2). However, whether this K(ATP) channel affects nitric oxide activation is unknown. Our aim was to assess whether pharmacologic activation of the K(ATP) channel by nicorandil contributes to endothelial nitric oxide synthase (eNOS) levels. A total of 21 7-week old male Sprague-Dawley rats were used. Seven were treated by intraperitoneal injection of nicorandil at 3 mg/kg/d; seven were treated with intraperitoneal nicorandil at 3 mg/kg/d after glibenclamide at 12 mg/kg/d twice a day p.o.; and seven were left untreated (controls). At 24 h after treatment, blood pressure and heart rate were measured, and eNOS, SUR2, Kir6.1, and Kir6.2 mRNA levels and eNOS protein levels in the left ventricle were determined by reverse transcription polymerase chain reaction (RT-PCR) and Western blot analysis. Nicorandil caused tachycardia without a change in blood pressure, whereas glibenclamide had no effect on the nicorandil-induced change in heart rate or on blood pressure. RT-PCR revealed that nicorandil increased the eNOS and SUR2 mRNA levels by 2.2- and 2.0-fold, respectively, (p< 0.01 versus control), and that these increases were completely inhibited by glibenclamide. A significant correlation was observed between eNOS and SUR2 mRNA levels in all experimental rats (r = 0.760, p < 0.001). However, Kir6.1 or 6.2 mRNA level was constant. Western blot analysis revealed that nicorandil caused a 1.6-fold increase in eNOS protein levels (p < 0.01 versus control). This increase was completely inhibited by glibenclamide. In conclusion, up-regulation of eNOS mRNA and protein levels by nicorandil, and inhibition of this upregulation by glibenclamide, were demonstrated in normotensive conscious rat hearts. Nicorandil appears to enhance cardiac eNOS expression via activation of a K(ATP) channel.