Hemodynamic benefits of celiac artery release for ruptured right gastric artery aneurysm associated with median arcuate ligament syndrome: a case report.

BACKGROUND: It has been reported that median arcuate ligament syndrome is closely associated with gastric or pancreaticoduodenal artery aneurysms. Hemodynamic state plays an important role in the formation of the aneurysms. These aneurysms are treated with open resection or endovascular exclusion. However, whether revascularization of the celiac artery can prevent the aneurysm formation is unknown. This report indicated a possibility that prophylactic revascularization for celiac artery stenosis resulted in decreased shear stress on the collaterals, which may otherwise be susceptible to new aneurysms. CASE PRESENTATION: This report describes a 51-year-old man who presented with epigastric pain at our hospital. According to contrast enhanced computed tomography (CT), he was diagnosed with a ruptured right gastric artery aneurysm and celiac artery stenosis caused by the median arcuate ligament (MAL). He had a vascular anomaly of the common hepatic artery arising from the superior mesenteric artery (SMA). His vital signs were stable. We informed him of the situation and he chose open surgery rather than endovascular treatment. Following, we resected the aneurysm and transected the MAL. Intraoperative angiography after transection of the MAL showed the antegrade blood flow to the splenic artery instead of the retrograde flow via the prominent collaterals. Follow-up CT confirmed narrowed collateral vessels between the SMA and the celiac artery without de-novo aneurysms. CONCLUSION: While the necessity of celiac artery release could be questioned, the present case supports the hemodynamic benefits of MAL transection in terms of de-novo aneurysm prevention.

Strength and Persistence of Energy-Based Vessel Seals Rely on Tissue Water and Glycosaminoglycan Content.

Vessel ligation using energy-based surgical devices is steadily replacing conventional closure methods during minimally invasive and open procedures. In exploring the molecular nature of thermally-induced tissue bonds, novel applications for surgical resection and repair may be revealed. This work presents an analysis of the influence of unbound water and hydrophilic glycosaminoglycans on the formation and resilience of vascular seals via: (a) changes in pre-fusion tissue hydration, (b) the enzymatic digestion of glycosaminoglycans (GAGs) prior to fusion and (c) the rehydration of vascular seals following fusion. An 11% increase in pre-fusion unbound water led to an 84% rise in vascular seal strength. The digestion of GAGs prior to fusion led to increases of up to 82% in seal strength, while the rehydration of native and GAG-digested vascular seals decreased strengths by 41 and 44%, respectively. The effects of increased unbound water content prior to fusion combined with the effects of seal rehydration after fusion suggest that the heat-induced displacement of tissue water is a major contributor to tissue adhesion during energy-based vessel sealing. The effects of pre-fusion GAG-digestion on seal integrity indicate that GAGs are inhibitory to the bond formation process during thermal ligation. GAG digestion may allow for increased water transport and protein interaction during the fusion process, leading to the formation of stronger bonds. These findings provide insight into the physiochemical nature of the fusion bond, its potential for optimization in vascular closure and its application to novel strategies for vascular resection and repair.

Spontaneous arterial calcification: a possible etiology for spontaneous splenic rupture in a patient on maintenance hemodialysis.

Spontaneous splenic rupture (SSR) is a rare condition in contrast to traumatic splenic hematoma, and vascular abnormality has rarely mentioned as an etiology in SSR with patients who had chronic kidney disease. We reported a 80-year-old female whose SSR might be related to splenic arterial calcification.

Moderate accumulation of calcium and phosphorus in the splenic artery with aging and low accumulation of those in the pulmonary artery with aging.

To elucidate compositional changes of the arteries with aging, the authors investigated age-related changes of elements in the splenic and pulmonary arteries, which supplied blood to contractile organs. After ordinary dissection by medical students at Nara Medical University was finished, the splenic and pulmonary arteries were resected from the subjects, ranging in age from 58 to 94 years. The element contents were determined by inductively coupled plasma-atomic emission spectrometry. It was found that a moderate accumulation of Ca and P occurred in the splenic artery with aging, but it hardly occurred in the pulmonary artery with aging. Regarding the relationship among elements, the finding that there were significant direct correlations among the contents of Ca, P, Mg, and Na was commonly obtained in both the splenic and pulmonary arteries. The accumulation of Ca and P in the splenic artery with aging occurred independently of that in the pulmonary artery. Histologic observation indicated that a major part of Ca deposits was seen in the middle tunica, but not in the internal tunica. Therefore, the calcification occurring in the splenic artery belonged to middle sclerosis.

Age-related changes of elements in thoracic and abdominal aortas and coronary, common carotid, pulmonary, splenic, common iliac, and uterine arteries and relationships in elements among their arteries.

To elucidate whether the accumulation of elements occurred simultaneously in the various arteries with aging, the authors investigated age-related changes of elements in the eight arteries, such as the thoracic and abdominal aortas and the coronary, common carotid, pulmonary, splenic, common iliac, and uterine arteries, and the relationships in the element contents among their arteries. After ordinary dissection by medical students was finished, the thoracic and abdominal aortas and the coronary, common carotid, pulmonary, splenic, common iliac, and uterine arteries were resected from the subjects, who ranged in age from 58 to 94 yr. The element contents were analyzed by inductively coupled plasma-atomic emission spectrometry. It was found that the accumulation of Ca was the highest in the common iliac artery and decreased in the order of the uterine artery, abdominal aorta, coronary artery, thoracic aorta, splenic artery, common carotid artery, and pulmonary artery. Regarding the relationships in the element contents among the eight arteries, it was found that there were significant direct correlations in the contents of Ca, P, Mg, Zn, Fe, and Na between the coronary and splenic arteries, and there were significant correlations in the contents of Ca, P, and Mg between the abdominal aorta and pulmonary artery.

[Expression of local angiotensinogen mRNA and activation of local nuclear factor-kappaB in vasculopathy of portal hypertension].

OBJECTIVE: To investigate the expression of local angiotensinogen mRNA and activation of local nuclear factor-kappaB in vasculopathy of portal hypertension and to discuss their role in the pathogenesis of portal hypertensive vasculopathy. METHODS: RT-PCR was used to detect the expression of local angiotensinogen mRNA in 28 specimens of splenic artery and vein obtained during operation of elective separation and amputation on 28 portal hypertension (PH) patients, 20 males and 8 females, aged 51.7 +/- 10 (30 - 65), and in 12 specimens of normal vessel from 12 patients undergoing splenectomy due to traumatic rupture of spleen. Chemiluminescent electrophoretic mobility shift assay (EMSA) was used to detect the activation of NF-kappaB in splenic artery and vein. RESULTS: The levels of local angiotensinogen mRNA in the splenic artery and vein of PH group were 0.48 +/- 0.21 and 0.43 +/- 0.16 respectively, both significantly higher than those in the control group (0.23 +/- 0.12 and 0.18 +/- 0.10, both P < 0.05). There was no significant difference between the splenic artery and vein in the expression of local angiotensinogen mRNA in PH group. The activation levels of NF-kappaB in splenic artery and vein of the PH patients were 1.44 +/- 0.23 and 1.38 +/- 0.18 respectively, both significantly higher than those of the control group (0.19 +/- 0.20 and 0.25 +/- 0.16 respectively, both P < 0.05). However, there was no significant difference in the activation levels of NF-kappaB between the splenic artery and vein in the PH patients (P > 0.05). CONCLUSION: Local angiotensinogen and activation of NF-kappaB maybe one of the factors in the pathogenesis of portal hypertensive vasculopathy, which can cause and advance portal hypertensive vasculopathy.

Immunohistochemical detection of apolipoprotein A-I and B-100 in canine atherosclerotic lesions.

We attempt to determine and compare the localization of apolipoproteins (apo) apoA-I and B-100 in atherosclerotic lesions of canine aortas, coronary arteries, and the peripheral arteries, using immunohistochemical techniques. Histopathologically, atherosclerotic lesions were characterized by deposition of lipids and infiltration of lipid-laden foamy cells in the tunica intima and tunica media, sometimes forming fibrofatty plaques containing abundant sudanophilic and mineralized material. Canine apoA (CapoA)-I and canine apoB (CapoB)-100 immunopositive signals were simultaneously observed in mild and severe atherosclerotic lesions of the aorta, coronary arteries, splenic arteries, and renal arteries in the double-immunolabeled sections. Both CapoA-I and CapoB-100 positive signals were seen in the cytoplasm of endothelial cells, smooth muscle cells, and macrophages. The subendothelial space and extracellular matrix in the tunica intima and media were also positive. Neither CapoA-I nor CapoB-100 positive signals were seen in normal arteries. These findings closely resemble those of the localization of apoA-I and apoB-100 in human atherosclerotic lesions.

Prejunctional AT(1) receptor subtype-dependent modification of neurotransmitter releases in canine isolated splenic arteries.

1. The regulation by angiotensin II (Ang II) formed locally on nerve-stimulated purinergic and adrenergic components of double-peaked vasoconstrictions in the canine splenic artery and Ang II receptor subtypes involved were investigated. 2. The perfusion of the precursor angiotensin I (Ang I, 0.1-1 nm) did not affect the vasoconstrictor responses to noradrenaline (NA, 0.03-1 nmol) and adenosine 5'-triphosphate (ATP, 0.03-1 micromol). The second component vasoconstrictor response to nerve stimulation was dose dependently potentiated by Ang I (0.1-1 nm). The first peaked constriction was slightly, but insignificantly increased. The potentiating effects of Ang I were abolished by KRH-594 (10 nm), a selective AT(1) receptor antagonist, but not by PD 123319 (1-10 nm), an AT(2) receptor antagonist. KRH-594 (10 nm) or PD 123319 (10 nm) never affected the vasoconstrictions to either NA or ATP. 3. The treatment with KRH-594 (1-10 nm) produced a greater inhibition on the second peaked response than the first one, although both of them were dose dependently inhibited. PD 123319 (1-10 nm) did not affect the vasoconstrictor responses induced by nerve stimulation. 4. Inhibition of angiotensin-converting enzyme with 10 nm enalaprilat reduced the second peaked response, having no significant inhibition on the first peaked response. A higher dose of enalaprilat (100 nm) produced a greater inhibition of the second peak than the first one. It reduced the second peak by approximately 65%, while the first peak was decreased approximately 35%. After treatment with enalaprilat, Ang I (1 nm) failed to enhance the neuronal vascular response. Enalaprilat at doses used did not affect the vasoconstrictions to either NA or ATP. 5. The present results indicate that endogenously generated Ang II may produce a more marked potentiation of adrenergic transmission than purinergic transmission via activation of prejunctional AT(1) receptors.

Antagonistic interaction between BIIE 0246, a neuropeptide Y Y2-receptor antagonist, and omega-conotoxin GVIA, a Ca2+ channel antagonist, in presynaptic transmitter releases in dog splenic arteries.

Isolated dog splenic arteries were perfused with Krebs-Henseleit solution at 37 degrees C, using the cannula inserting method. Periarterial nerve electrical stimulation (10-V amplitude; 1-ms duration; 30-s trains of pulses; 1, 4 and 10 Hz) readily caused double peaked vasoconstrictions, i.e., 1st peaked response was mostly inhibited by alpha,beta-methylene ATP and the 2nd one, by prazosin. These responses were consistently inhibited by omega-conotoxin GVIA (omega-CTX), whereas they were facilitated by BIIE 0246, a neuropeptide Y (NPY) Y2-receptor antagonist. The omega-CTX-induced blocking effects of transmitter release were significantly antagonized by BIIE 0246. It is possible that the NPY Y2 receptor activity may partially be linked to presynaptic Ca2+ channels.

Pathological morphology alteration of the splanchnic vascular wall in portal hypertensive patients.

OBJECTIVE: To investigate the pathological morphology alteration of the splanchnic vascular wall in portal hypertensive patients. METHODS: Splenic arteries, veins and gastric coronary veins from portal hypertensive patients (n = 50) were removed during esophagogastric devascularization with splenectomy and were observed under optic and electron microscopes. The expression of iNOS in the splenic artery wall was analysed with immunohistochemistry. RESULTS: The internal elastic membrane and medial elastic fibers of the splenic artery wall were broken and degenerated. Atrophy, apoptosis and phenotypic changes were seen in smooth muscle cells of splenic arteries. Positive staining for iNOS was seen in the cytoplasm of smooth muscle cells and iNOS activity was elevated compared with the non-cirrhotic patients (P < 0.01). In the splenic and gastric coronary veins of cirrhotic patients, we found proliferative intima, extensive thrombi adhering to the venous wall, mimicked arteriosclerosis plaques accompanied with hypertrophy of smooth muscle cells, and thickened muscle fibers of veins with increase in extracellular matrix. CONCLUSION: Portal hypertension may be complicated by splanchnic arterial and venous vasculopathy. There may be an interactive relationship among portal hypertension, splanchnic hyperdynamic disturbances and splanchnic vasculopathy in the pathogenesis of portal hypertension.

Chlamydial infection in canine atherosclerotic lesions.

We attempted to detect chlamydial antigens in canine atherosclerotic lesions from seven dogs by immunohistochemical technique using anti-Chlamydia psittaci (C. psittaci) polyclonal and anti-C. pneumoniae monoclonal antibodies. Immunopositive signals to both antibodies were recognized in the atherosclerotic lesions of the aortas, coronary and splenic arteries of all dogs. Positive signals were found in the foamy cytoplasm of infiltrated macrophages and extracellular matrices in the lesions. In some lesions, cytoplasm of the endothelial cells and smooth muscle cells was also immunopositive against both antibodies. By electron microscopy, chlamydial microorganisms were found in the cytoplasm of endothelial cells and smooth muscle cells. Using polymerase chain reaction (PCR), detection of C. pneumoniae DNAs were performed in the spleen, heart (coronary arteries) and kidney in one of the seven dogs. Positive 314 bp PCR products were obtained in all samples of the dog. These results confirmed the presence of viable Chlamydiae in atheromas and supported the conclusion that the organism may be an active factor in the pathogenesis of canine, as well as human atherosclerosis.

Immunohistochemical detection of apolipoprotein B-100 and immunoglobulins (IgA, IgM, IgG) in the splenic arteries of aging dogs.

Accumulation of lipids and hyalinosis in the splenic arteries of aged dogs are frequently detected by routine histopathologic examinations. The purpose of this study was to pinpoint the localization of canine apolipoprotein B-100 (CApoB-100) and immunoglobulins (IgA, IgM, IgG) in the splenic arteries of aging dogs (n = 80) through the use of immunohistochemical techniques. CApoB-100 deposits were found in the subendothelial space, extracellular matrix, and atheromatous lesions in the tunica media of the arteries in dogs > or = 6 years of age. Foamy cytoplasm of the infiltrated macrophages was also CApoB-100 immunopositive. In dogs > or = 10 years of age, almost all central arteries were CApoB-100 immunopositive. Hyaline deposits within the wall were characterized by immunopositivity against canine IgA, IgM, IgG, and albumin. Lipid accumulation in splenic arteries may be an age-related lesion and a precursor of the atheromatous plaques associated with splenic hemorrhage and infarcts later in life. In addition, deposition of immunoglobulins, probably mediated by immune complexes, may play an important role in the development of canine vascular diseases similar to human disease.

Dissociation of potentiation of Leu31 Pro34 neuropeptide Y on adrenergic and purinergic transmission in isolated canine splenic artery.

The present study observed the effects of an activation of neuropeptide Y (NPY) Y1 receptors on adrenergic and purinergic components of double-peaked vasoconstrictor responses to periarterial nerve stimulation in the isolated, perfused canine splenic arteries. The results showed that 3-30 nM Leu31 Pro34 neuropeptide Y (LP-NPY) produced a dose-dependent potentiation of double-peaked vasoconstrictor responses to trains of 30-s pulses at 1, 4 or 10 Hz of stimulation. The potentiation of LP-NPY of the nerve-stimulated vasoconstrictions were completely inhibited by subsequent blockade of alpha1-adrenoceptors or Y1 receptors with 0.1 microM prazosin or with 1 microM BIBP 3226 ((R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininami de), respectively. The remaining responses in the presence of LP-NPY and prazosin were abolished by P2X receptor desensitization with 1 microM alpha,beta-methylene ATP. Moreover, 30 nM LP-NPY failed to modify the vasoconstrictor responses to nerve stimulation after treatment with prazosin. A subsequent administration of alpha,beta-methylene ATP completely suppressed the remaining responses after prazosin and LP-NPY. The vasoconstrictions induced by 0.003-1 nmol noradrenaline and 0.003-1 micromol ATP were slightly, but not significantly enhanced by 30 nM LP-NPY. The observations indicated that activation of postjunctional NPY Y1 receptors may have an important role in the modulation of adrenergic rather than purinergic transmission of the sympathetic co-transmission.

Pharmacological evidence for the presence of a peripheral postjunctional D2-like dopamine receptor in rabbit splenic artery.

1. This study was designed to investigate the involvement of postjunctional D2-like receptors in a rabbit vasculature model used to evaluate the D1-like agonist activity. Dopamine, epinine and (-)-DP-5,6-ADTN, three mixed D1/D2-like agonists, fenoldopam and SKF 82958, two selective D1-like agonists and SKF 89124, a selective D2-like agonist, were administered cumulatively in precontracted and alpha/beta-blocked rabbit splenic artery rings in order to evaluate their D1-like-mediated vasorelaxant activity before and after pretreatment with the selective D2-like antagonist YM 09151-2 (1 nM). 2. Dopamine (pD2=6.35+/-0.09), epinine (pD2=6.73+/-0.13), (-)-DP-5,6-ADTN (pD2=7.56+/-0.09) and SKF 82958 (pD2=8.55+/-0.10) reversed completely the U46619-induced contracture whereas SKF 89124 was inactive up to 10 microM and fenoldopam acted like a partial agonist (pD2=8.31+/-0.09, alpha=0.62). The selective D2-like dopamine receptor antagonist YM 09151-2 (1 nM) significantly (P<0.05) potentiated the vasorelaxant activity of dopamine (pD2=7.01+/-0.07), epinine (pD2=7.14+/-0.08), (-)-DP-5,6-ADTN (pD2=8.19+/-0.09) and SKF 89124 (40% relaxation at 10 microM), whereas it did not alter the effects of fenoldopam (pD2=8.40+/-0.09, alpha=0.68) and SKF 82958 (pD2=8.58+/-0.08). 3. The D2-like antagonist YM 09151-2 induced the same degree of effect with all the substances tested in both endothelium-denuded and endothelium-intact preparations. 4. The selective D2-like dopamine receptor agonist SKF 89124 did not produce any intrinsic effect on the splenic artery, but was able to produce a rightward shift of the forskolin-induced relaxation. 5. The results of these experiments support the existence of a non-endothelial postjunctional D2-like dopamine receptor counteracting the D1-like-mediated vasodilatation in rabbit splenic artery, probably by the inhibition of adenylate cyclase.

Prominent sympathetic purinergic vasoconstriction in the rabbit splenic artery: potentiation by 2,2'-pyridylisatogen tosylate.

1. Vasoconstrictions induced by transmural electrical field stimulation were frequency-dependent from 2 to 32 Hz in the rabbit isolated splenic artery. All contractions were abolished in the presence of tetrodotoxin 1 microM or guanethidine 100 microM. Stimulation at a frequency of more than 32 Hz induced both neurogenic and myogenic responses. 2. Prazosin (1 microM) did not significantly affect vascular contractions to electrical stimulation. Desensitization of P2X-purinoceptors with alpha, beta-methylene ATP (alpha, beta-meATP, 3 microM) abolished the contractions to stimulation at 2-8 Hz and inhibited more than 80% of the vascular response at 16 Hz, but it did not significantly change the responses at 32 Hz. Contractile responses at 32 Hz were inhibited by a combination of prazosin and alpha, beta-meATP. Effects of pyridoxal-phosphate-6-azophenyl-2', 4'-disulphonic acid tetrasodium salt (a selective P2X-purinoceptor antagonist) and suramin (a competitive P2-purinoceptor antagonist) on the neurogenic responses were investigated in this study. 3. 2,2'-Pyridylisatogen tosylate (PIT, 0.3-3 microM) significantly potentiated the vasoconstrictions to electrical stimulation at 2-32 Hz in a concentration-dependent manner. Potentiated responses were restored to the control level 30 min after washing. Concentration-dependent response curves for noradrenaline (NA) or alpha, beta-meATP were not significantly changed by 3 microM PIT, and vasoconstriction by adenosine 5'-triphosphate (ATP, 300 microM) was unaffected by PIT. Coomassie brilliant blue-G (1 microM), which shares the potentiating effect on a recombinant P2Y-purinoceptor with PIT (King et al., 1996), did not inhibit or potentiate the purinergically-mediated component of the response to sympathetic nerve stimulation. The selective alpha 2-adrenoceptor antagonist yohimbine (1 microM) also potentiated the vascular responses to electrical stimulation. 4. The present results indicate that ATP evokes postjunctional contractile responses at low and high frequency electrical stimulation of sympathetic nerves supplying the rabbit splenic artery. PIT potentiates the responses to sympathetic (purinergic) nerve stimulation; this appears to be mainly via prejunctional rather than postjunctional actions.

Histochemical analysis of acidic glycoconjugates in the endothelium lining the splenic blood vessels in the rat.

An electron microscopic analysis with specific histochemical stainings for acidic glycoconjugates was carried out to examine the endothelium lining blood vessels of the rat spleen. Histochemical staining performed was the postembedding high or low iron diaminethiocarbohydrazide-silver protein-physical development (HID or LID-TCH-SP-PD) method, with or without prior digestion with acidic glycoconjugate-degrading enzymes, such as heparitinase, testicular hyaluronidase, chondroitinase B and neuraminidase. The results indicated that the acidic glycoconjugates in the basal lamina of the endothelial cells lining the four types of blood vessel (central arteries, arterial capillaries, splenic sinuses and pulp veins) were heparan sulfate, chondroitin sulfate A and/or C, chondroitin sulfate B and sialic acid residues. In the endothelial cells lining the central arteries, arterial capillaries and pulp veins, the surface coat of the luminal plasma membrane included heparan sulfate, chondroitin sulfate A and/or C, chondroitin sulfate B and sialic acid residues, whereas the corresponding ultrastructure of the splenic sinuses was devoid of detectable amounts of acidic glycoconjugates. This suggests that such characteristic histochemical features of the endothelium in the four types of the splenic blood vessel can be related to the possible physiological functions of the spleen.

The relationship between density of alpha-adrenoceptor binding sites and contractile responses in several porcine isolated blood vessels.

1. The aim of this study was to investigate constrictor alpha-adrenoceptors in three isolated blood vessels of the pig, the thoracic aorta (TA), the splenic artery (SA) and marginal ear vein (MEV) and then compare the functional response with the densities of alpha 1- and alpha 2-adrenoceptor binding sites in these and several other porcine vascular tissues, palmar common digital artery (PCDA), palmar lateral vein (PLV) and ear artery (EA). 2. Noradrenaline (NA), phenylephrine (PE) and UK14304 (all at 0.03-10 microM) elicited concentration-dependent contractions in the TA and MEV, with a rank order of potency of UK14304 > NA > PE. UK14304 produced maximal responses which were 58% (TA) and 65% (MEV) of that of NA. In the SA, UK14304 and PE produced maximal responses which were less than 10% and 50% of the NA-induced maximal response respectively, with an order of potency of NA > PE. In the SA, NA-induced contractions were competitively antagonized by prazosin (pA2 = 8.60 +/- 0.15). Further, rauwolscine (1-10 microM) antagonized NA-induced contractions with an apparent pKB of 6.09 +/- 0.11 (n = 6), indicating an action at alpha 1-adrenoceptors. The combination of the two antagonists at concentrations selective for alpha 1- (0.1 microM) and alpha 2-adrenoceptors (1 microM) had no greater effect than either antagonist alone. This suggests that the SA expresses only post-junctional alpha 1-adrenoceptors. 3. In the TA, prazosin produced non-parallel shifts in the NA-induced CRC and this was also observed with rauwolscine, where reductions in the maximal responses were also observed. In the MEV, prazosin was largely inactive in antagonizing NA-induced contractions. In both these vessels a combination of these two antagonists had a greater effect than either alone, indicating the presence of functional alpha 1- and alpha 2-adrenoceptors. The post-junctional alpha 2-adrenoceptors in all of these vessels were resistant to prazosin, suggesting the alpha 2-adrenoceptor to be of the alpha 2A/2D subtype. The expression of functional alpha 2-adrenoceptors was MEV > TA > PLV > PCDA > SA. 4. In radioligand binding studies using TA P2 pellet membranes, [3H]-prazosin and [3H]-RX821002 ([1,4-[6,7(n)-3H] benzodioxan-2-methoxy-2-yl)-2-imidazole) labelled different high affinity sites, and in competition studies using identical membranes corynanthine displaced [3H]-prazosin with 10 fold higher affinity than rauwolscine, indicating that [3H]-prazosin was selectively binding to alpha 1-adrenoceptor sites. Further, rauwolscine displaced [3H]-RX821002 with approximately 100 fold greater affinity compared to corynanthine, which is indicative of selective alpha2-adrenoceptor binding.5. Separation of the P2 pellet into plasma membrane and mitochondrial fractions was carried out using a differential sucrose density gradient. [3H]-prazosin and [3H]-RX821002 binding sites were found in both the plasma membrane and mitochondrial fractions.6. In saturation studies all tissues produced single site saturation curves with no difference in the Kd(range 0.13-0.20nM) of the alpha1-adrenoceptor sites for [3H]-prazosin. However, there was considerable variation in Bmax of alpha 1-adrenoceptor sites; the highest density was found in the TA (397.9 =/- 52.7 fmol mg-1, n = 4), followed by the PCDA (256.7 +/- 22.7 fmol mg-1, n = 4), the PLV and SA having approximately equal density (143.6 +/- 3.9 and 159.1 +/- 7.0 fmol mg-1 respectively, n = 4 for both), followed bythe EA (91.3 +/- 10.5 fmol mg-1, n = 3) and the MEV had the lowest density (48.9 +/- 11.4 fmol mg-1,n = 3).7. In saturation studies using [3H]-RX821002, all tissues produced single site saturation curves with no differences in the Kd values (range 1.31 +/- 2.16 nM) but the highest densities were found in the TA and MEV (545.3 +/- 36.2 and 531.0 +/- 40.9 fmol mg-1 respectively), followed by the PLV (418.4 +/- 39.4 fmol mg-1), then the EA (266.3 +/- 40.0 fmol mg-1), and low densities of [3H]-RX821002 binding being found in the PCDA and SA (155.9 +/- 18.1 and 117.5 +/- 19.3 fmol mg-1 respectively).8. The pattern of binding site distribution for alpha l- and alpha 2-adrenoceptors is in reasonable agreement with functional studies carried out in these porcine vascular tissues; the TA has the highest densities of alpha 1-and alpha2-adrenoceptors; in the SA and PCDA there is a predominance (although small) of alpha l-adrenoceptor binding sites, the reverse of which is observed both in the PLV and MEV (i.e. greater density of alpha2-adrenoceptor sites). Thus, it would appear that alpha 1- and alpha2-adrenoceptor densities play a role in the expression of functional responses via these receptor subtypes; although it is interesting to note that the SA did have a small density of alpha 2-adrenoceptor binding sites, no functional response was observed after alpha2-adrenoceptor activation.

Guanidino succinic acid is not the endogenous source of endothelium-derived relaxing factor in the porcine isolated splenic artery.

The possibility that guanidino succinic acid is the major endogenous source of endothelium-derived relaxing factor has been examined using the porcine isolated splenic artery. Administration of 100 microM NG-nitro-L-arginine methyl ester (L-NAME) caused a substantial, endothelium-dependent contraction of the splenic artery that was inhibited by L-arginine (1 mM) but was unaffected by D-arginine (1 mM). L-NAME enhanced the responsiveness of the splenic artery to 5-hydroxytryptamine in endothelium-intact segments only, and the potentiating action of L-NAME was inhibited by L-arginine but not by D-arginine. Administration of 100 microM guanidino succinic acid did not relax the splenic artery and it did not inhibit or reverse contractions of the splenic artery induced by L-NAME. Administration of guanidino succinic acid, either before or after L-NAME, did not affect the potentiating action of L-NAME on the 5-hydroxytryptamine-induced contraction of the splenic artery in endothelium-intact segments. Although substance P caused an endothelium-dependent relaxation of preconstricted segments of the splenic artery, guanidino succinic acid did not relax preconstricted, endothelium-intact or endothelium-denuded segments of the artery. L-NAME inhibited the relaxation induced by substance P in endothelium-intact preparations. The findings for the effects of arginine are consistent with L-arginine being a source of endothelium-derived relaxing factor in the porcine splenic artery, while observations with guanidino succinic acid indicate that it is not a substrate for the synthesis of endothelium-derived relaxing factor in this blood vessel.

The influence of monoamine oxidase activity on the release of noradrenaline by tyramine.

The influence of monoamine oxidase (MAO) activity on the kinetic characteristics of noradrenaline (NA) release evoked by tyramine has been examined. Dog splenic artery strips were incubated with [3H]NA after inhibition of catechol-O-methyl-transferase (COMT) and of extraneuronal uptake. In some experiments MAO was also inhibited. The strips were then perifused for 200 min. Some strips were exposed to tyramine (1.5, 40 and 3240 mumols L-1) from the 100th to the 200th min of perifusion. In control experiments (i.e. in the absence of tyramine) most of the [3H]NA accumulated in the strips (83% of tissue activity) and did not contribute to the efflux. The value of this "bound fraction" (the NA located at a site(s) from which it could not be displaced by a simple concentration gradient) was the same whether or not MAO was inhibited. At all concentrations, tyramine mobilized only one NA compartment. Increasing the concentration of tyramine resulted in a decrease of the "bound fraction", which became negligible for the highest concentration of tyramine used (3240 mumols L-1), regardless of MAO being inhibited or not. However, for the lower concentrations of tyramine, MAO inhibition resulted in an increase in the amine's releasing effect. The formation of 3,4-dihydroxy-phenylglycol (DOPEG) increased with increase of tyramine from the 1.5 to 40 mumols L-1 concentration, but not beyond. The ratio NA/DOPEG increased for all concentrations of tyramine. Thus, it was not possible to exclude an inhibitory effect of tyramine on MAO activity with the highest concentration used.

An unusually important role of O-methylation in the disposition of noradrenaline and adrenaline by the dog renal artery.

Using the oil immersion technique, the role of neuronal uptake, monoamine oxidase and COMT in the inactivation of 2 concentrations (0.23 and 2.3 mumol/l) of noradrenaline and adrenaline was determined by the prolongation of the inactivation time caused by cocaine (12 mumol/l), pargyline (1 mmol/l) and U-0521 (50 mumol/l), respectively. The results obtained allow us to conclude that: 1) as previously shown, for the saphenous vein and mesenteric artery, noradrenaline is inactivated more rapidly than adrenaline; 2) in all tissues and for both concentrations of noradrenaline and adrenaline, neuronal uptake is more important for the inactivation of noradrenaline than for that of adrenaline, while O-methylation is more important for the inactivation of adrenaline than for that of noradrenaline. The only exception is that in the renal artery, O-methylation is very clearly the most important pathway of inactivation for both concentrations of both amines.