摘要:

The effects of anion substitution, pH and extracellular Mg2+ concentration on 28Mg accumulation were examined in rabbit aortic smooth muscle. Accumulation of 28Mg (expressed as a 28Mg/Mg2+ ratio) was not changed when the concentration of added, nonradioactive MgCb was increased from 1.5 to 15.0 mM. The 28Mg efflux rate was increased by added MgCh (0.15, 0.5 or 1.5 mM) in a dose-related manner after a similar delay of 5–10 min. Addition of 1.5 mM MgCl2, MgSO4 or magnesium aspartate hydrochloride enhanced 28Mg efflux and inhibited accumulation of 28Mg to the same extent. An increase or decrease in extracellular pH correspondingly increased or decreased 28Mg accumulation. However, the 28Mg efflux rate was not altered when extracellular pH was decreased. Efflux of 28Mg was increased by added 1.5 mM MgCl2 at pH 7.4 but not at pH 5.8. Thus, the net uptake of Mg2+ appears to be proportional to the concentration of extracellular Mg2+ in rabbit aorta. Low external pH decreases 28Mg retention in rabbit aorta by inhibiting the uptake of 28Mg rather than by increasing 28Mg efflux. Effects of added Mg2+ on transmembrane movements of 28Mg are not altered by changes in the associated anion. Extracellular Mg2+ appears to enter the cell and exchange with an intracellularly located pool of 28Mg in the same manner, regardless of whether the accompanying anion is sulfate, chloride or monoaspartate hydrochlorid

ISSN:1018-1172    

DOI:10.1159/000158755

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The effects of successive, norepinephrine (NE)-stimulated, contractions of porcine carotid artery intima-media strips as a function of recovery medium were studied. Recovery following NE stimulation required the presence of glucose in the bathing medium for subsequent force production in response to NE stimulation. Potassium stimulation following failed NE contractions produced maximal contractions. Phosphorous nuclear magnetic resonance studies under similar conditions indicated that the energy state of the tissue was not impaired during and after recovery from NE stimulation without glucose. This study shows that the phasic phase of norepinephrine-stimulated contractions is dependent on the availability of extracellular glucose during the poststimulation recovery period for successive NE contractions.

ISSN:1018-1172    

DOI:10.1159/000158756

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The effect of substance P on leukocytes and platelets in rabbit skeletal muscle microvasculature was studied by intravital microscopy and electron microscopy. Local application of substance P caused vasodilatation and formation of aggregates of platelets and leukocytes in postcapillary venules with subsequent migration of leukocytes through the vessel wall. Many neutrophils were partially degranulated. Aggregate formation induced by substance P could not be prevented by autacoid antagonists. However, superfusion with calcitonin gene-related peptide prior to challenge with substance P greatly inhibited aggregate formation and leukocyte extravasation.

ISSN:1018-1172    

DOI:10.1159/000158757

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The medio-adventitial border of a variety of perfusion-fixed arteries of young adult rabbits, guinea pigs and rats has been studied in the electron microscope. The arterial media in the different vessels ranged from 2 to 25 cells thick. Neuromuscular junctions, defined as axon varicosities containing synaptic vesicles closely apposed to the outer surface of smooth muscle cells, with only a single layer of basal lamina intervening between axon and muscle membranes, were identified in all three species. Junctions were found in most vessels < 1 mm in diameter with a frequency ranging from 8,000–150,000 junctions per square millimeter of smooth muscle surface, the number generally increasing with decreasing arterial diameter. These small arteries were mostly, but not exclusively, muscular rather than elastic. In large arteries, such as abdominal aortae and some elastic arteries lying close to the heart (e.g. the carotid), no junctions were found. In a few vessels, such as guinea pig basilar (muscular) and rat and guinea pig superior mesenteric (elastic) arteries, junctions were found infrequently (1,000–4,000/mm2). The data indicate that all muscular arteries in rats and guinea pigs, and most muscular arteries in rabbits, receive innervation in the form of sympathetic neuromuscular junctions. Whilst a few elastic vessels are sparsely innervated with junctions, some are surrounded by axon bundles containing vesicle-filled varicosities. The physiological significance of the latter is obsc

ISSN:1018-1172    

DOI:10.1159/000158758

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

Lymph flow and lymphatic pressure fluctuations were measured in cannulated popliteal efferent lymphatics of the sheep. Five-minute intra-arterial infusions of norepinephrine (0.4 µg/kg/min) produced up to fivefold increases in lymph flow and lymphatic contraction frequency. This effect was blocked by the α-antagonist phentolamine but not by the P-antagonist propranolol. Isoproterenol (0.4 µg/kg/min i.a.) inhibited flow. This effect was antagonized by propranolol. Acetylcholine (0.4 µg/kg/min) had little effect on lymph flow. Since norepinephrine and isoproterenol respectively stimulate and inhibit lymphatic pumping activity in vitro, it is proposed that the effects of these agents on lymph flow and lymphatic contraction frequency in vivo are best explained by direct modulatory actions on the lymphatic smooth muscle p

ISSN:1018-1172    

DOI:10.1159/000158759

出版商:S. Karger AG    

年代:1989

数据来源: Karger

摘要:

The effects of a DAi dopamine receptor selective agonist, fenoldopam, were examined on human blood vessels. Fenoldopam relaxed precontracted human arteries in vitro from brachial, cerebral, cervical, colic, coronary, lumbar, pulmonary, renal and splenic sites. Fenoldopam failed to relax uterine or external iliac arteries or saphenous vein segments. These effects of fenoldopam were not endothelium dependent, but were antagonised by the selective DAi receptor antagonists, SCH 23390, (+)-butaclamol, and (R)- more than (S)-sulpiride. The effect of fenoldopam may involve cyclic adenosine monophosphate. These studies indicate the presence of DAi receptors on a variety of large isolated human arteries.

ISSN:1018-1172    

DOI:10.1159/000158760

出版商:S. Karger AG    

年代:1989

数据来源: Karger

ISSN:1018-1172    

DOI:10.1159/000158761

出版商:S. Karger AG    

年代:1989

数据来源: Karger