摘要:

There is now compelling evidence indicating that there is a greater sympathetic innervation of blood vessels in the spontaneously hypertensive rat (SHR) when compared with the innervation of corresponding vessels in the normotensive genetic control rat (WKY). In selected vascular beds in the SHR, increased sympathetic innervation occurs immediately after birth and prior to the expression of hypertension in the animal. In contrast, the available evidence suggests that the sympathetic innervation of cardiac tissue in SHR and WKY are similar in young and adult rats. The functional significance of the enhanced sympathetic innervation of blood vessels in the SHR with regard to the development or maintenance of hypertension relates in two ways to the well-established phenomena of vascular smooth muscle cell hypertrophy and hyperplasia, which are thought to be the pathophysiological basis for the increased peripheral vascular resistance and elevated blood pressure in this animal model of hypertension. First, the enhanced innervation of blood vessels in the SHR leads to an augmented release of the vasoconstrictor transmitter noradrenaline (NA). The predicted consequences of this augmented release of NA upon vascular contraction are modulated by the presence of a larger number of sites for neuronal inactivation (i.e. reuptake sites) of NA by virtue of the presence of the increased innervation. Second, and of more significance, is the inter-relationship between hypernoradrenergic innervation and vascular smooth muscle hyperplasia, as the early appearance of such changes is a powerful indicator for the subsequent expression of hypertension in the SHR. In view of the substantial evidence that implicates vascular smooth muscle cells in regulating the degree of their sympathetic innervation and confirms the influence of sympathetic nerves upon vascular smooth muscle hyperplastic change, attention is drawn to the role of trophic factors in providing the setting for the development of hypertension in the SHR.

ISSN:1018-1172    

DOI:10.1159/000158748

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Experiments were designed to analyze the difference in endothelium-dependent responsiveness to acetylcholine between arteries and veins. The effect of endothelium-derived relaxing factor(s) released from femoral arteries of the dog was compared on the coronary artery of the dog, the aorta of the rat, and portal-mesenteric veins of both species. Endothelium-derived relaxing factor(s) released by canine femoral arteries induced comparable relaxation of the canine coronary artery and the aorta of the rat. However, neither the canine nor the rat portal vein relaxed when exposed to endothelium-derived relaxing factors) released by the femoral arterial segments. Endothelium-derived relaxing factor(s) did not affect the action potentials and the spontaneous activity of the rat portal vein. Sodium nitroprusside induced complete relaxation of the canine coronary artery but failed to abolish the spontaneously evoked contractions of the portal veins. These experiments suggest that the longitudinal smooth muscle of portal veins is insensitive to endothelium-derived relaxing factor(s), presumably because of a different sensitivity of guanylate cyclase. Endothelium-derived relaxing factor does not possess calcium-entry blocking properties.

ISSN:1018-1172    

DOI:10.1159/000158749

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The distribution of serotonin-like immunoreactive (5-HT-LI) fibers in pial arteries and arteries of the choroid plexus in the cat, rat and guinea pig was examined. Weak 5-HT-LI fibers were observed in cerebral arteries when these arteries were fixed by immersion after they had been dissected from the exsanguinated animals. The 5-HT-LI fibers, however, were not detected in arteries when they were fixed in situ or in vitro after they had first been perfused with phosphate-buffered saline (PBS) or Krebs solution in situ to flush the blood components from the lumen prior to dissection. In these arteries, 5-HT-LI fibers with intense immunofluorescence could however be demonstrated following incubation with serotonin (5-HT) in vitro. The distribution patterns of 5-HT-LI fibers and catecholamine fluorescence fibers were found to be similar. Following bilateral superior cervical ganglionectomy, 5-HT-LI fibers were not detected in pial vessels even after incubation with 5-HT. Light-microscopic autoradiographic examination of [3H]-5-HT uptake in pial arteries showed that silver grain granules were concentrated only in the unmyelinated nerve profile in the adventitial layer. No uptake of [3H]-5-HT into smooth muscle cells and endothelial cells was found. The neuronal uptake of [3H]-5-HT was blocked by imipramine. Results from ultrastructural studies also showed that 5-HT-like immunoreactivities were found only in the axoplasm and were never detected following chronic superior cervical ganglionectomy. These results indicate that the presence of 5-HT-containing nerves in pial vessels in various species examined is due to the uptake of 5-HT into sympathetic nerves, and further support our hypothesis that cerebral pial vessels do not receive authentic serotonergic innervation. The present study also identifies the heterogeneity in characteristics of smooth muscle and endothelial cells among cerebral and peripheral arteries.

ISSN:1018-1172    

DOI:10.1159/000158750

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158751

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158752

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Cytochrome P-450 is the terminal oxidase of the electron transport chain in the endoplasmic reticulum. Arachidonic acid (AA) can be oxidatively metabolized by cytochrome P-450 hemoproteins to an array of compounds identified as constituents of tissues and biological fluids. Their synthesis can be manipulated by pharmacologic probes and are altered in pathophysiologic conditions. These novel eicosanoids stimulate release of peptide and steroid hormones, inhibit platelet and leukocyte aggregation, influence Na+-K+-ATPase and alter vasomotor tone. They also participate in fluid and electrolyte homeostasis, stimulus-secretion coupling, and regulation of tissue blood flow. Since these novel AA metabolites may participate in receptor-mediated signal transduction, and have been implicated in the generation of second messengers and changes in intracellular calcium, these studies have important implications for understanding basic biological mechanisms.

ISSN:1018-1172    

DOI:10.1159/000158753

出版商:S. Karger AG    

年代:1989

数据来源: Karger