calcimycin and Subarachnoid-Hemorrhage

Although abnormalities in the control of endothelial vasomotility have been reported in both experimental and clinical studies, the mechanism of the endothelial dysfunction that occurs following subarachnoid hemorrhage (SAH) remains unclear. Because of the absence of previous in vivo studies of endothelial function in cerebral vessels in response to SAH or cerebral vasospasm, the authors investigated endothelium-dependent responses in an established primate model of vasospasm after SAH. Endothelial function was assessed by examining vascular responses to intracarotid injections of various drugs known to act via the endothelium. Drugs that have a rapid total body clearance were selected so that their pharmacological effects would be limited to the cerebral circulation after an intracarotid infusion.. Seventeen adult male cynomolgus monkeys were used. Cerebrovascular endothelium-dependent responses were examined in control animals and in animals with SAH 7, 14, and 21 days after placement of a subarachnoid clot around the right middle cerebral artery. Cortical cerebral blood flow (CBF) and cerebrovascular resistance (CVR) were recorded continuously during 5-minute intracarotid infusions of 5% dextrose vehicle, acetylcholine, histamine, bradykinin, or Calcimycin. In control animals the intracarotid infusion of acetylcholine produced a significant (7.8 +/- 9.5%) increase in CBF and a 9.3 +/- 8.7% reduction in CVR in comparison with a control infusion of dextrose vehicle. The responses to acetylcholine disappeared in animals 7 days post-SAH, specifically in the subset of animals in which arteriography confirmed the presence of vasospasm. Infusion of Calcimycin produced no significant changes in CBF or CVR in control animals, but resulted in a significant reduction in CBF and increase in CVR in animals 7 days after SAH and in animals with vasospasm. An infusion of histamine or bradykinin had no significant effect on CBF or CVR.. An intracarotid infusion of acetylcholine, but not one of histamine, bradykinin, or Calcimycin, produced a measurable physiological response in the normal primate cerebrovasculature. Cerebral vasospasm that occurred after SAH produced a pathophysiological effect similar to the endothelial denudation shown in the in vitro experiments of Furchgott and Zawadzki, in which acetylcholine constricted the vessels via activation of receptors on smooth-muscle cells. Changes in vascular responses to acetylcholine and Calcimycin in animals with vasospasm, compared with control animals, provide evidence that endothelial dysfunction plays a key role in the development and/or sustenance of vasospasm after SAH.

Topics: Acetylcholine; Animals; Bradykinin; Calcimycin; Endothelium, Vascular; Histamine; Macaca fascicularis; Male; Models, Animal; Subarachnoid Hemorrhage; Vasodilation; Vasodilator Agents; Vasospasm, Intracranial

We investigated the changes in endothelial function of pulmonary as well as basilar artery after experimental subarachnoid hemorrhage (SAH) induced by cisternal blood injection in rabbits. The animals were killed on day 2 and day 7, and the mechanical responses were determined on transverse strips of the main pulmonary artery and rings harvested from the basilar artery. To examine the role of the vagal nerve, we cut the left vagal nerve immediately before injecting cisternal blood. Relaxation response of pulmonary and basilar arteries to acetylcholine (ACh) and A23187 were abolished after endothelial removal and reality inhibited by either NG-nitro-L-arginine (NOARG) or methylene blue (MB). Indomethacin failed to modify these relaxation responses. Relaxation response of the main pulmonary artery strips to ACh was significantly (p < 0.05 and p < 0.01) attenuated on day 2 in 6 of 12 rabbits. In the remaining 6 rabbits, relaxation was not affected. No change in relaxation responses to A23187 and sodium nitroprusside (SNP) was observed in any of the 12 cases. In the vagotomized rabbits no decreased response to ACh was observed. On day 7, relaxation response to ACh returned to normal. ACh also produced decreased relaxation in basilar artery rings on day 2 with no change in A23187- and SNP-induced relaxation. Contractile responses of pulmonary and basilar arteries to norepinephrine (NE), endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT), and U46619 were not affected after SAH. These results suggest that less functional muscarinic receptors that produce/release less endothelium-derived relaxation factor [EDRF/nitric oxide (NO)] are involved in causing the reduced relaxation of pulmonary and basilar arteries after SAH and the vagal nerve may play a role in regulating the receptor-mediated, endothelium-dependent relaxation in the main pulmonary artery after experimental SAH.

Topics: Acetylcholine; Animals; Basilar Artery; Calcimycin; Endothelin-1; Endothelium, Vascular; Male; Nitroprusside; Pulmonary Artery; Rabbits; Subarachnoid Hemorrhage; Vagotomy; Vasodilation

Despite growing clinical use of transluminal balloon angioplasty (TBA) to treat cerebral vasospasm after aneurysmal subarachnoid hemorrhage (SAH), the precise mechanism of action of balloon dilation on the cerebral arterial wall is unknown. In this experiment the authors examined the pharmacological and morphological changes in 10 normal and 12 vasospastic canine basilar arteries following in vitro silicone microballoon TBA. For the SAH group in which the double-hemorrhage model was used, vasospasm was confirmed by angiography and the animals were killed on Day 7 after the first SAH. In vitro TBA was performed on basilar arteries from normal and SAH dogs immediately after sacrifice and removal of the brain. The procedure was performed while the arteries were maintained in oxygenated Krebs buffer. In the pharmacological studies, potassium chloride, prostaglandin F2 alpha, serotonin, and noradrenaline were used as vasoconstrictors, and bradykinin and calcium ionophore A23187 were used to produce an endothelium-dependent dilation. In both normal and vasospastic groups, the pharmacological responses of dilated segments of basilar arteries were compared to those of nondilated segments of the same arteries. Vessels from all groups were examined using scanning electron microscopy (EM) and transmission EM. Scanning EM was used to study the intact vessel wall, the smooth-muscle cell layer obtained after digestion with hydrochloric acid, and the extracellular matrix obtained after digestion with bleach. Cross-sections of the vessel wall were examined using transmission EM. The most striking finding was that immediately after in vitro TBA of both normal and vasospastic canine basilar arteries, there was a significant reduction (p < 0.05) of responses to both vasoconstrictors and vasorelaxants. As revealed by scanning EM and transmission EM, both normal and vasospastic vessels dilated with TBA showed flattening and patchy denudation of the endothelium, and straightening and occasional rupturing of the internal elastic lamina. In addition, vasospastic vessels dilated with TBA showed decreased surface rippling and mild stretching and straightening of smooth-muscle cells, and mild thinning of the tunica media. There was no gross vascular disruption or obvious change in the extracellular matrix of the vessel walls of either normal or vasospastic arteries after TBA. These results suggest that functional impairment of vasoreactivity in the vessel wall as a result of mechan

Topics: Analysis of Variance; Angioplasty, Balloon; Animals; Basilar Artery; Bradykinin; Calcimycin; Collagen; Dinoprost; Dogs; Dose-Response Relationship, Drug; Elastin; Endothelium, Vascular; In Vitro Techniques; Ischemic Attack, Transient; Microscopy, Electron; Microscopy, Electron, Scanning; Muscle, Smooth, Vascular; Norepinephrine; Potassium Chloride; Radiography; Serotonin; Subarachnoid Hemorrhage; Vasoconstriction; Vasodilation

Experiments were designed to determine the effect of subarachnoid hemorrhage on endothelium-dependent relaxations in small arteries of the brain stem. A "double-hemorrhage" canine model of the disease was used, and the presence of vasospasm in the basilar artery was confirmed by angiography.. Secondary branches of both untreated basilar arteries (inner diameter, 324 +/- 11 microns; n = 12) and arteries exposed to subarachnoid hemorrhage for 7 days (inner diameter, 328 +/- 12 microns; n = 12) were dissected and mounted on glass microcannulas in organ chambers. Changes in the intraluminal diameter of pressurized arteries were measured using a video dimension analyzer.. In untreated arteries, 10(-11) to 10(-7) M vasopressin, 10(-10) to 10(-6) M bradykinin, and 10(-9) to 10(-6) M calcium ionophore A23187 caused endothelium-dependent relaxations. At 10(-6) and 3 x 10(-4) M the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) abolished relaxations to vasopressin and produced small but significant rightward shifts of the concentration-response curves to bradykinin and A23187. At 10(-3) M L-arginine prevented the inhibitory effect of L-NAME. Subarachnoid hemorrhage abolished relaxations to vasopressin but did not affect relaxations to bradykinin or A23187.. These studies suggest that in small arteries of the brain stem vasopressin causes relaxations by activation of the endothelial L-arginine pathway. This mechanism of relaxation is selectively inhibited by subarachnoid hemorrhage. Preservation of endothelium-dependent relaxations to bradykinin and A23187 is consistent with the concept that small arteries are resistant to vasospasm after subarachnoid hemorrhage.

Topics: Animals; Arginine; Arterioles; Bradykinin; Brain Stem; Calcimycin; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Endothelium, Vascular; Female; Male; NG-Nitroarginine Methyl Ester; Subarachnoid Hemorrhage; Vasodilation; Vasopressins

Autologous blood was injected into the cisterna magna of mongrel dogs twice with an interval of 48 hours. They were killed 3 days, 1 week, or 4 weeks after the first injection of blood, and helical strips of the basilar artery were prepared. Contractions induced by 5-hydroxytryptamine, noradrenaline, prostaglandin F2 alpha, and oxyhemoglobin were significantly potentiated. Relaxations caused by nicotine, K+, arachidonic acid, and prostaglandin I2 were suppressed, but the relaxant response to calcium ionophore A23187 and substance P did not change significantly. These results suggest that contractions mediated via activation of alpha, 5-hydroxytryptamine, and prostaglandin F2 alpha receptors are potentiated, and relaxations caused by stimulation of vasodilator nerves and by endogenous and exogenous prostaglandin I2 are attenuated in dog basilar arteries exposed to subarachnoid clot. On the other hand, certain relaxations possibly mediated by endothelium-derived relaxing factor do not appear to be significantly influenced.

Topics: Animals; Arachidonic Acid; Arachidonic Acids; Basilar Artery; Calcimycin; Disease Models, Animal; Dogs; Female; In Vitro Techniques; Ischemic Attack, Transient; Male; Neurotransmitter Agents; Nicotine; Oxyhemoglobins; Potassium; Prostaglandins; Subarachnoid Hemorrhage; Vasoconstriction

Chronic cerebral vasospasm was induced in 16 monkeys by direct placement of a clot of autologous blood over the arteries of the circle of Willis on the right side. The middle cerebral arteries (MCA's) on the clot side all showed angiographic vasospasm, which was maximal 7 days after subarachnoid hemorrhage. Animals were sacrificed at this time and vascular responses to acetylcholine (ACh), histamine, and the calcium ionophore A23187 were studied in MCA rings from the clot (spastic) side and the non-clot (control) side. In control preparations with an intact endothelium, which had been precontracted by prostaglandin F2 alpha (PGF2 alpha), histamine and A23187 produced significant relaxation. The same concentrations of histamine and A23187 did not relax vascular tissues in which the endothelium had been mechanically removed. Acetylcholine did not produce a significant endothelium-dependent relaxation of primate MCA rings, but did relax rings of primate common carotid artery. Pretreatment with chlorpheniramine (an H1-receptor antagonist) prevented histamine-induced relaxation; however, cimetidine (an H2-receptor antagonist) had no inhibitory action. It thus seems that histamine mediates relaxation of intact MCA's mostly by an H1-receptor-mediated release of endothelium-derived relaxing factor (EDRF). Relaxations induced by histamine and A23187 in MCA's from the clot side were substantially reduced. Moreover, the small component of ACh-induced relaxation was also abolished. Endothelium-independent relaxation induced by glyceryl trinitrate (GTN) occurred in arteries from both the control and the clot sides. Constrictions induced by KC1 and PGF2 alpha were reduced on the clot side of the MCA's. These results suggest that subarachnoid hemorrhage influences both the generation of EDRF and the constriction of affected arteries. The small contraction which was elicited in spastic arteries was fully relaxed by GTN.

Topics: Acetylcholine; Animals; Calcimycin; Cerebral Angiography; Cerebral Arteries; Endothelium, Vascular; Histamine; Ischemic Attack, Transient; Macaca fascicularis; Nitric Oxide; Nitroglycerin; Receptors, Histamine H1; Subarachnoid Hemorrhage; Vasodilation

To investigate the alteration of endothelium-dependent responses in chronic vasospasm after subarachnoid hemorrhage (SAH), experiments were carried out in the double-hemorrhage canine model. After the presence of vasospasm was confirmed by cerebral angiography on Days 0 and 7, pharmacological studies on the basilar artery were conducted in vitro on Day 8. In the SAH group, endothelium-dependent relaxation was abolished in response to arginine vasopressin and was significantly reduced in response to thrombin. Endothelium-independent relaxation in the SAH group was preserved in response to papaverine and was minimally reduced in response to sodium nitroprusside. Endothelium-dependent contraction in response to arachidonic acid, acetylcholine, the calcium ionophore A23187, adenosine diphosphate, mechanical stretching, and hypoxia persisted in the SAH group. The maximal contraction to KCl and uridine triphosphate, which is endothelium-independent, was diminished in the SAH group, but not changes in sensitivity were noted in the concentration-response relationships. A significant correlation was observed between the degree of vasospasm determined angiographically and the loss of endothelium-dependent relaxation. The loss of endothelium-dependent relaxation and the persistence of endothelium-dependent contraction suggest that the deterioration in the endothelium-dependent responses may be an important component in the pathogenesis of cerebral vasospasm.

Topics: Animals; Basilar Artery; Biological Products; Calcimycin; Dogs; Dose-Response Relationship, Drug; Endothelium; Female; Ischemic Attack, Transient; Male; Nitric Oxide; Nitroprusside; Subarachnoid Hemorrhage; Vasoconstriction; Vasodilation