Superoxide dismutase reduces the impairment of endothelium-dependent relaxation in the spontaneously hypertensive rat aorta.

The involvement of the superoxide anion in endothelium-dependent relaxation (EDR) was examined in noradrenaline-contracted aortic smooth muscle preparations isolated from normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). Acetylcholine (ACh, 10(-9)-10(-5) M) induced EDR in both WKY and SHRSP preparations in a concentration-dependent manner, but with a significantly smaller amplitude in those from SHRSP than in those from WKY. The ACh-induced EDR was inhibited by N(omega)-nitro-L-arginine (L-NOARG), in a concentration-dependent manner, both in WKY and SHRSP.

Abnormal response to ryanodine in oesophageal striated muscle of spontaneously hypertensive rats.

The effects of ryanodine on twitch contraction and basal tension of oesophageal striated muscle were compared between preparations from stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar Kyoto rats (WKY). Ryanodine (3 x 10(-7) M) augmented the twitch contraction in WKY preparations, butt attenuated it in SHRSP preparations. Rates of contraction and relaxation of twitch contraction, normalized to developed tension, were slightly decreased by ryanodine in both preparations.

[Endothelium-derived factors in hypertensive blood vessels, especially nitric oxide and hypertension].

Endothelium-dependent relaxation (EDR) in the blood vessels of spontaneously hypertensive rats (SHR) and the role of nitric oxide (NO) in the initiation of hypertension are reviewed. EDR was impaired in blood vessels of SHR depending on age and degree of hypertension when compared with those of normotensive rats. The cause of the impairment varied among the type of blood vessels: a decrease in the production of NO and endothelium-derived relaxing factor (EDRF) and an increase in the production of endothelium-derived contracting factor (EDCF) are the main causes of the impairment in large arteries, while a decrease in endothelium-dependent hyperpolarization and increased release of EDCF are the main causes of the impairment in small arteries.

Contraction of arterial smooth muscle of normotensive and spontaneously hypertensive rats by manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP).

Manganese(III)tetrakis(1-methyl-4-pyridyl)porphyrin (MnTMPyP), which has been known as a cell permeable superoxide dismutase mimetic, induced concentration-dependent contraction in rat carotid artery acting directly on smooth muscle. The contractile action was more prominent in the preparation from stroke-prone spontaneously hypertensive rats (SHRSP) compared with that from Wistar Kyoto rats (WKY). It was abolished by the removal of extracellular Ca(2+) or the application of verapamil.

Effects of L-arginine on spontaneous contraction of the rat portal vein.

The effects of L-arginine on spontaneous contraction of endothelium-denuded longitudinal preparations of the rat portal vein were studied. L-arginine increased the frequency of spontaneous contraction concentration-dependently between 10 microM and 1 mM. Changes in contraction amplitude and duration were not remarkable.

Reduced effect of caffeine on twitch contraction of oesophageal striated muscle from stroke-prone spontaneously hypertensive rats.

1. There are known differences in the sensitivity to caffeine between skeletal muscle (soleus) of normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The present study was performed in order to examine differences in the effects of caffeine on twitch contraction between visceral striated muscle using the outer layer of the oesophagus from WKY rats and stroke-prone SHR (SHRSP).

Caffeine-induced contracture in oesophageal striated muscle of normotensive and hypertensive rats.

To elucidate whether properties of the sarcoplasmic reticulum are altered, not only in vascular smooth muscle, but also in visceral striated muscle of spontaneously hypertensive rats (SHR), caffeine-induced contractures in oesophageal striated muscle of Wistar Kyoto rats (WKY) and stroke-prone SHR (SHRSP) were compared. In both preparations, 30 mM caffeine induced a contracture with two components. The second component, which was diminished by extracellular Ca(2+) removal or Ni(2+) but not by verapamil, was much smaller in SHRSP.

Endothelium-dependent relaxation in pulmonary arteries of L-NAME-treated Wistar and stroke-prone spontaneously hypertensive rats.

To evaluate whether the elevated blood pressure induced by chronic treatment with N(omega)-nitro-L-arginine methyl ester (L-NAME) contributes to an impairment of endothelium-dependent relaxation (EDR), the effects of chronic treatment of Wistar rats with L-NAME on systolic blood pressure, pulmonary arterial blood pressure and EDR of the pulmonary arteries were studied and compared with those of stroke-prone spontaneously hypertensive rats (SHRSP). While the systolic blood pressure (SBP) of Wistar rats was increased above that of controls by chronic treatment with L-NAME, it was still significantly lower than that of SHRSP. Chronic treatment with L-NAME did not affect pulmonary arterial blood pressure.

Responses to endothelium-derived factors and their interaction in mesenteric arteries from Wistar-Kyoto and stroke-prone spontaneously hypertensive rats.

1. Responses to endothelium-derived nitric oxide (EDNO), indomethacin-sensitive endothelium-derived contracting factor (EDCF) and hyperpolarization by endothelium-derived hyperpolarizing factor (EDHF) and the interaction among these factors in mesenteric arteries from 16-week-old Wistar Kyoto (WKY) rats and age-matched stroke-prone spontaneously hypertensive rats (SHRSP) were studied, observing the time-course of the response to 10-5 mol/L acetylcholine (ACh). 2.

Effects of flufenamic acid on smooth muscle of the carotid artery isolated from spontaneously hypertensive rats.

Endothelium-removed carotid artery strips from stroke-prone spontaneously hypertensive rats spontaneously developed a tonic myogenic contraction. Flufenamic acid reduced the resting tone observed during superfusion with Tyrode's solution, in a concentration-dependent manner. Flufenamic acid also inhibited contractions produced by high-K solutions in a concentration-dependent manner.

Unaltered caffeine-induced relaxation in the aorta of stroke-prone spontaneously hypertensive rats (SHRSP).

Caffeine-induced relaxation was studied in aortic segments from Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). Although acetylcholine-induced endothelium-dependent relaxation was impaired in preparations from SHRSP, the relaxation induced by caffeine was identical in both groups. In addition, caffeine-induced relaxation was not affected by removal of the endothelium in either group.