Effect of cooling on vascular smooth muscle response to endothelin-1 in human and rat veins.

BACKGROUND: The plasma level of endothelin-1 is locally increased during cooling but the net vasoconstrictor effect will be dependent on temperature effects on the vascular smooth muscle reactivity in response to the polypeptide. The aim of this study was to investigate the effect of cooling on the vascular smooth muscle response to endothelin-1 in human and rat veins. METHODS: Registration of vascular smooth muscle activity in vitro in vessel preparations from normal subjects. SETTING: Laboratory. PATIENTS AND ANIMALS: Superficial hand veins from 14 patients undergoing hand surgery and external jugular veins from 14 rats. INTERVENTIONS: Effects of endothelin-1, after denudation of the endothelium and during cooling, were compared with controls without these interventions. RESULTS: At 37 degrees C, endothelin-1 induced a concentration-dependent contraction in the human hand and rat jugular veins. The sensitivity to endothelin-1 was enhanced in segments without endothelium. At 37 degrees C, no relaxation in response to endothelin-1 was observed. Cooling to 10 degrees C did not alter precontraction achieved by endothelin-1 at 37 degrees C in the human hand veins, while it depressed the precontraction in the rat jugular vein. The effect of cold was reversible. Removal of the endothelium did not alter the response to cooling. CONCLUSIONS: The maintained reactivity in response to endothelin-1 during cooling of the human vessels suggests that the reported increase in endothelin-1 levels due to local cooling could contribute in the pathophysiology of peripheral vasospasm in humans.

Non-specific steroidal esterase activity and distribution in human and other mammalian tissues.

An NADPH dependent arylamine carcinogen and fatty acid steroid ester metabolizing esterase activity belonging to the B- or carboxylesterase class of non-specific esterase (EC 3.1.1.1) was measured by two different methods: (i) a spectrophotometric assay using alpha naphthyl acetate (ANA) as substrate and (ii) a radiometric method using the conversion of beclomethasone-17,21-dipropionate to beclomethasone-17-monopropionate as the endpoint. The two methods were strongly correlated when assayed in human mononuclear leukocytes (r = 0.89, P < 0.0001) and human mammary tissue (r = 0.91, P < 0.0001). Hence it was concluded that the two substrates are metabolized at least in part by the same enzyme. This esterase activity was abundant in human monocytes, present in T-lymphocytes and equally divided between CD4 and CD8 T-lymphocyte subsets. The same activity was expressed in human liver, colon, stomach, breast and brain tissues. The distribution of this esterase in human tissues showed high activity in liver, intermediate activity in colon, stomach and breast and low activity in brain tissue. The interorgan distribution observed in human tissues was closely mimicked when the esterase activity was assessed in liver, colon and brain tissues from three mouse strains and three rat strains. The non-specific steroidal esterase activity determined by ANA metabolism in human mammary tissue was shown to be reproducible when assayed as triplicate samples from each of 16 different women (intraclass correlation coefficient 67.3%, P < 0.03). The interindividual variation in mammary tissue was high (18.4-fold) and there was a positive correlation between the esterase activity and age (r = 0.58, P < 0.01), as well as a tendency toward bimodal distribution. To our knowledge, these data represent the first systematic study of interorgan and interspecies comparisons of a non-specific steroidal esterase activity.

Endothelial relaxing 5-hydroxytryptamine receptors in the rat jugular vein: similarity with the 5-hydroxytryptamine1C receptor.

Serotonin (5-HT) at low concentrations induces an endothelium-dependent relaxation in the rat jugular vein mediated via a 5-HT1-like receptor. The receptor mediating this relaxation was characterized in vitro using agonists and antagonists in segments precontracted with prostaglandin F2 alpha in the presence of the 5-HT2 receptor antagonist ketanserin. The following substances acted as agonists, with the order of potency: 5-HT > dl-alpha-methyl-5-hydroxytryptamine = 5-carboxamidotryptamine > quipazine > 8-hydroxy-2-(dl-n-propylamino) tetralin. dl-Propranolol, mesulergine and mianserin acted as competitive, methysergide, 6-methyl-1-(1-methylethyl)-ergoline-8 beta-carboxylic acid 2-hydroxy-1-methylpropyl ester and sumatriptan as non-competitive, and ritanserin acted as both a competitive and non-competitive antagonist of the 5-HT-induced relaxation. Neither the 5-HT2 antagonists ketanserin and spiperone nor the 5-HT3 antagonist 1 alpha-H,3 alpha,5 alpha-H-tropan-3-yl,3,5-dichlorbenzoate affected the 5-HT-induced relaxation. The pEC50 values of the agonists and the pA2 and pAh values of the antagonists correlated strongly with pKD values at the 5-HT1C binding site. These results are consistent with a peripheral vascular 5-HT1C receptor in the rat jugular vein.

Heterogeneity of contractile 5-HT receptors in human hand veins.

To increase our knowledge of human peripheral vasospasm we characterized the contractile 5-hydroxytryptamine (5-HT) receptors in human superficial hand vein segments in vitro. The 5-HT1 receptor agonist, sumatriptan, the 5-HT2 receptor agonist, dl-alpha-methyl-5-HT, and the 5-HT3 receptor agonist, 2-methyl-5-HT, all induced concentration-dependent contractions. The contractile response to sumatriptan was antagonized by the non-selective 5-HT receptor antagonist, methiothepin, but was unaffected by the 5-HT2 receptor antagonist, ketanserin. The contractile response to dl-alpha-methyl-5-HT was antagonized by both methiothepin and ketanserin. The contraction elicited by 2-methyl-5-HT was not affected by the 5-HT3 receptor antagonist, MDL 72222, but was antagonized by ketanserin. The results suggest that serotonergic contraction in the human superficial hand vein involves both 5-HT1 and 5-HT2 but not 5-HT3 receptors. Such receptor heterogeneity in human blood vessels should be considered when using drugs and when designing future compounds for medical use.

Differential effect of hypothermia on the vascular tone and reactivity of the human coronary artery and graft vessels.

Hypothermia may contribute to vascular spasm during bypass surgery. The effect of cooling on the reactivity of the human coronary artery (CA), saphenous vein (SV) and internal mammary artery (IMA) was studied in vitro. In CA and IMA cooling diminished the resting tension and the contraction to potassium, noradrenaline and 5-hydroxytryptamine. In contrast, in SV the contraction to noradrenaline and 5-hydroxytryptamine was augmented by cooling. The effect of cold was reversible. These results demonstrate different effects of hypothermia in CA and the graft vessels. Thus, hypothermia augments the receptor-mediated contraction in SV but depresses it in IMA which thereby resembles CA. The difference is most marked in the contractile response to 5-hydroxytryptamine, which may accumulate during surgery. This may contribute to spasm in the saphenous vein grafts and may be involved in the mechanisms responsible for the inferior patency of SV compared to IMA as a graft vessel.

5-Hydroxytryptamine receptor profile in healthy and diseased human epicardial coronary arteries.

STUDY OBJECTIVE: The aim of the study was to investigate the receptor events that mediate the vascular effects of 5-hydroxytryptamine (5-HT) on human coronary arteries, since 5-HT has long been thought to play a role in coronary artery vasospasm. DESIGN: Recently available selective receptor agonists and antagonists were used to examine the 5-HT receptor subtypes present in human epicardial coronary arteries using in vitro organ baths. EXPERIMENTAL MATERIAL: 138 segments of coronary arteries were obtained from 21 patients aged 2-66 years undergoing heart transplantation. MEASUREMENTS AND MAIN RESULTS: 5-HT produced only concentration dependent contractions of coronary artery segments. No evidence was obtained for 5-HT receptors mediating either endothelium dependent or endothelium independent vasorelaxation. In tissue from patients without ischaemic heart disease, 5-HT effects were mimicked by (+/-)-alpha-methyl-5-HT (alpha-me-5-HT), a selective agonist at 5-HT2 receptors. In addition, the selective 5-HT1-like receptor agonist GR43175 produced contractions which achieved 30% of the maximum response to 5-HT. Responses to alpha-me-5-HT were surmountably antagonised by the non-selective antagonist methiothepin (0.1 mumol.litre-1) as well as the 5-HT2 receptor antagonist ketanserin (0.1 mumol.litre-1). In contrast GR43175 effects were resistant to blockade by ketanserin, but remained sensitive to methiothepin. Responses to the two agonists were not antagonised by the 5-HT3 receptor antagonist MDL72222 (1.0 mumol.litre-1). Vessel segments from ischaemic heart disease patients also contracted to alpha-me-5-HT and GR43175. Diseased arteries contracted with a decrease in the maximal response induced by both alpha-me-5-HT and by 90 mM K+ depolarisation compared to "normal" vessels, but the effect of GR43175 was preserved in the diseased arteries. Vascular rings adjacent to an atheromatous lesion were more reactive to GR43175 than serial segments taken distal to the lesion. CONCLUSIONS: These results show that both 5-HT1-like and 5-HT2 receptors mediate contraction of human epicardial coronary arteries and indicate that effects mediated by 5-HT1-like receptors but not 5-HT2 receptors are preserved in patients with ischaemic heart disease.

Effect of cooling on smooth muscle response to 5-hydroxytryptamine in human hand veins.

5-Hydroxytryptamine has been suggested to be a mediator in peripheral cold-induced vasospasm. In order to investigate the contribution of different 5-hydroxytryptamine receptor subtypes in the contractile response during cooling, segments of subcutaneous hand veins obtained from 50 patients undergoing hand surgery were examined in vitro in organ baths. The temperature in the bath was initially 37 degrees C and was either continuously lowered to 10 degrees C or kept constant at 37 degrees C, 29 degrees C. Cooling to 25 degrees C augmented the contractile response to 5-hydroxytryptamine in intact as well as in endothelium-denuded segments. The 5-hydroxytryptamine2 receptor antagonist ketanserin antagonized the contractile response to 5-hydroxytryptamine at 37 degrees C, and in addition abolished the cold-induced enhancement of the response during cooling. This points to a major role of the 5-hydroxytryptamine2 receptor in the cold-induced augmentation of the response to 5-hydroxytryptamine, which was further supported by increased contractions to the 5-hydroxytryptamine2 receptor agonist alpha-methyl-5-hydroxytryptamine during cooling. Contractile responses were also obtained by the selective 5-hydroxytryptamine1-like receptor agonist GR43175 interpreted to indicate the presence of a smaller 5-hydroxytryptamine1-like receptor population. However, the response to GR43175 was unaffected by cooling. These results warrant further investigations of the role of 5-hydroxytryptamine in cold-induced peripheral vasospasm.

Cooling enhances alpha 2-adrenoceptor-mediated vasoconstriction in human hand veins.

The contribution of different receptor subtypes in the contractile response during cooling in human hand vessels is of considerable interest in the understanding of cold-induced peripheral vasospasm as it appears in Raynaud's phenomenon. Subcutaneous vein segments from 50 patients undergoing hand operations not related to vascular disorders were examined in vitro. The temperature in the organ bath was initially 37 degrees C and was either continuously lowered to 10 degrees C or kept constant at 37 degrees C, 29 degrees C or 20 degrees C. The characteristics of the alpha-adrenoceptor-mediated motor response were elucidated with the use of the alpha 1-antagonist, prazosin, and the alpha 2-antagonist, yohimbine. A great variability between individuals in the proportions of alpha 1- and alpha 2-adrenoceptors was found. In the majority of the vessels continuous cooling to 25 degrees C augmented a noradrenaline-induced contraction. This augmentation was unaltered in the presence of prazosin but abolished by yohimbine, suggesting that it was mediated via the alpha 2-adrenoceptor. In the remaining vessels with a predominating alpha 1-adrenoceptor-mediated response a cold-induced relaxation was registered. This could be the result of a reduced alpha 1-adrenoceptor-mediated contraction at this low temperature. These varying reactions to cooling were unaffected by the beta-antagonist, propranolol, and by endothelial denudation. The results obtained in corresponding experiments with the alpha 1-agonist methoxamine and alpha 2-agonist, oxymetazoline, were conflicting, probably due to the poor selectivity of these agonists in human tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Cooling augments contractile response to 5-hydroxytryptamine via an endothelium-dependent mechanism.

The interaction between cooling and vasoactive substances, e.g. 5-hydroxytryptamine (5-HT), plays an important role in the pathophysiology of cold-induced vasospasm. Our objective was to study the effect of cooling on the 5-HT vascular response, classify the involved 5-HT receptors, and to analyze the role of the endothelium. Ring segments from the rat jugular vein, a preparation without alpha-adrenergic receptors, were suspended in organ baths to record the circular motor activity. The temperature was initially 37 degrees C and was thereafter either continuously lowered to 10 degrees C or kept constant at different temperatures within this range. 5-HT at low concentrations (10(-11) to 3 x 10(-8) M) induced relaxation at 37 degrees C in segments precontracted by prostaglandin F2 alpha. The relaxation was recognized to be mediated via an endothelium-dependent 5-HT1-like receptor mechanism presumably involving the release of endothelium-derived relaxing factor (EDRF). Cooling to 29 and 20 degrees C diminished the relaxation, probably due to an attenuated release of EDRF. 5-HT at concentrations of more than 10(-8) M induced a contraction in all vessels at 37 degrees C mediated via a 5-HT2 receptor. An increased 5-HT-induced contraction was seen at temperatures below 37 degrees C in vessels with an intact endothelium. Endothelial denudation diminished the cold-induced enhancement of the contraction to 5-HT. These studies suggest that endothelial mechanisms contribute to a cold-induced augmented response to 5-HT.

Beneficial effects of intra-arterial reserpine after upper-extremity embolectomy: a prospective randomised trial.

Persistent ischaemia occasionally follows technically-successful arterial embolectomy, and has generally been ascribed to small-vessel thrombosis in the distal vascular bed. Because of the possibility that distal vasospasm might be a contributory cause, we conducted a prospective randomised trial of vasodilator therapy in this setting. In 50 consecutive patients presenting with their first episode of upper-extremity arterial embolism, we compared the results of the intra-arterial instillation of 0.5 mg reserpine with those of saline alone following embolectomy. Among 29 patients receiving saline only, 13 (44.8%) suffered persistent or recurrent limb ischaemia requiring reoperation, while three (14.3%) of 21 patients receiving reserpine had continuing ischaemia (P = 0.02). Three patients in each group required a second re-operation; all three in the reserpine group were ultimately found to have a proximal axillo-subclavian artery stenosis as the cause for their persistent or recurrent limb ischaemia. Although its underlying pathophysiology remains obscure, peripheral vasospasm appears to accompany acute embolic arterial occlusion. Manoeuvres to prevent or reverse such distal vasoconstriction may be useful in avoiding persistent or recurrent ischaemia following arterial embolectomy.

Effect of long-term ketanserin treatment on 5-HT levels, platelet aggregation and peripheral circulation in patients with Raynaud's phenomenon. A double-blind, placebo-controlled cross-over study.

The long-term effects of the serotonergic (5-hydroxy-tryptamine, 5-HT) receptor antagonist, ketanserin, on 5-HT levels in whole blood, platelet aggregation and peripheral circulation were investigated in a double-blind placebo-controlled cross-over study. In 13 patients with Raynaud's phenomenon, 5-HT and catecholamine levels in whole blood were determined and platelet aggregation assayed after addition of ADP, collagen and 5-HT. Peripheral circulation was evaluated with fingertip temperatures and finger plethysmography before and after local cooling, with measurements repeated after indirect sympathetic blockade by body warming and after alcohol. Patients' symptoms were continuously registered in an individual diary. All measurements were performed 8 to 12 hours after the last drug intake. Five of seven scleroderma patients reported beneficial effects of ketanserin treatment and all six patients with primary Raynaud's phenomenon reported less severe and shorter cold-induced attacks. 5-HT levels in whole blood were significantly reduced after 5 weeks of ketanserin treatment (p less than 0.001) with a tendency for persistence of this reduction after halting of the medication (a "carry-over" effect). Platelet aggregation velocity induced by ADP, collagen and 5-HT was unaffected after ketanserin treatment. The diastolic blood pressure in these patients was decreased from 77.5 mmHg to 71.0 mmHg (p less than 0.001) after ketanserin, but the finger systolic blood pressure (FSBP) was unchanged. After sympathetic blockade by body warming, patients with ketanserin treatment had a paradoxical reduction in both FSBP and finger-tip temperatures, which makes a supposed alpha-receptor-blocking effect of ketanserin less likely. The reduced 5-HT levels in whole blood may explain the subjective favourable effect on patients with Raynaud's phenomenon.

The objective diagnosis of vibration-induced vascular injury.

For 44 patients with vibration-induced white finger and a reference group of 25 healthy men, finger systolic blood pressure (FSBP) before and after local cooling, skin temperature, and rewarming rates were determined before and after vasodilation (body warming and alcohol). An estimation of the proportions of vasopasm and organic changes was possible, and cutaneous changes could be separated from changes in the main digital vessels. The arm blood pressure was higher for the patients and the fingertip temperatures were lower, but both normalized after vasodilation. The FSBP values were equal in the two groups before local cooling. Afterward the patients had lower FSBP values which remained unchanged after the postvasodilatation cooling. Ten patients, all smokers, reacted with complete arterial closure after local cooling. When this group was separated from the other smoking patients, there was no significant difference between the smoking and nonsmoking patients, and the FSBP differences between the patients and referents was almost eliminated. It was concluded that, in vibration-exposed patients, injuries to skin circulation seem to be more frequent than injuries to the main digital vessels, except for some smokers, who have severe vasopasm combined with organic changes.

Serotonergic mechanisms in isolated human peripheral arteries and veins.

Isolated arteries and veins from the hand and mesentery of healthy human subjects were studied in vitro. Serotonin caused contraction with an intrinsic activity approximately equal to that of norepinephrine and epinephrine in mesenteric and hand arteries and veins. Ketanserin inhibited the response to serotonin in a competitive, probably partly irreversible manner in the mesenteric vessels and the hand arteries. In the hand veins, ketanserin counteracted the serotonin-induced contraction in a noncompetitive way.

Adrenergic and serotoninergic mechanisms in human hand arteries and veins studied by fluorescence histochemistry and in vitro pharmacology.

Isolated hand arteries and veins from healthy human subjects were tested in vitro for their contractile response to adrenergic agonists and 5-hydroxytryptamine (5-HT) under standardized conditions. This allowed for quantitative estimation of various receptor characteristics. The relative sympathomimetic potency suggested alpha-adrenergic receptors, which was confirmed in Schild plots following phentolamine antagonism of the response (pA2 for artery 7.57, for vein 7.75). 5-HT contracted with a relative potency approximately equal to noradrenaline and adrenaline in arteries, but only one fifth to one tenth of the catecholamine activity in veins. Ketanserin inhibited the 5-HT response in a competitive, probably also irreversible, manner in arteries (pA2 9.50, KA 8.90 X 10(-7) M). In the veins, ketanserin counteracted the 5-HT-induced contraction in a noncompetitive way.

Indications for angiography and its optimal performance in patients with Raynaud's phenomenon.

Fifty-two patients with Raynaud's phenomenon of the upper extremity were examined by angiography because of suspected organic stenosis or occlusions in areas available for reconstructive vascular surgery. Different vasodilatating treatments were compared either singly or combined: blockade of the brachial plexus, intraarterial injections of phentolamine or reserpine, body warming, and orally administered alcohol. Body warming in combination with 4 mg phentolamine gave optimal vasodilatation within the shortest time and without vasospasm after local cold provocation in patients with sympathetically induced vasospasm, enabling a clear visualization of organic lesions. A proper vasodilatation was also obtained after blockade of the brachial plexus or reserpine injection combined with body warming, but not until 40 min after the start of the treatments.

Analysis of vasospasm in hand arteries by in vitro pharmacology, hand angiography and finger plethysmography.

1. The distribution of sympathetic nerves in hand arteries and veins from 18 normal subjects was studied by microscopy according to the Falck-Hillarp histofluorescence method for the cellular visualization of cathecholamines and by quantitative analysis of noradrenaline with a radioenzymatic method. Segments of hand arteries and veins were tested in vitro for the vasomotor effect of sympathomimetic agonists. 2. Fluorescence microscopy revealed a plexus of noradrenaline-containing nerve fibres surrounding both arteries and veins. The concentration of noradrenaline in the walls were 4.5-4.7 ng/mg protein. The relative agonist potency was characteristic for alpha-receptors. Phentolamine produced parallel shift of the dose-response curves both for arteries and veins. 3. Finger plethysmography with local cold provocation down to 10 degrees C was performed in the patients with traumatic vasospastic disease before and after inhibition of the sympathetic nervous system by body warming and orally administered alcohol. Four patients had undisturbed circulation, as revealed by the ratio between the systolic blood pressure in the arm and in the finger in conjunction with cold provocation tests. 13 patients had vasospasm of varying degrees, and 3 patients suffered from organic stenosis. 4. Hand angiography was performed before and after local cold provocation. The patients with organic stenosis did not show vasodilatation after 4-6 mg phentolamine injection. Patients with true vasospasm responded, in addition, with efficient vasodilatation 15 min after reserpine injection, which also abolished the cold-induced vasospasm.