The recording of venous compliance in the conscious dog: a method for the assessment of venoconstrictor agents

A review of methodologies evaluating superficial vein properties in viv: focus on compliance and reactivity

The saphenous vein (SV) is a hindlimb superficial vein which has aroused a considerable interest because of its implication in chronic venous disease and its use in coronary artery or lower limb bypass grafts. The morphology and patency of the SV are commonly assessed for diagnosis and management, but the dynamic properties of the vein - compliance, elasticity and reactivity, less widely studied, are also fundamental issues. The subject of this review is neither to review the pathologies, nor the treatments or surgical procedures. The goal is to gather together all existing types of investigation on the superficial vein and to focus on the dynamic venous properties in vivo. The data collected indicate that plethysmography (PG) and ultrasound (US) are extensively used to evaluate SV patency, reflux and morphology. Their use to evaluate superficial vein compliance is less widespread but highly necessary. The protocols used via venous occlusion are described and the various parameters used to accurately measure compliance and distensibility versus elasticity are presented and discussed. The advantage of US diameter measurement is shown, including additional pulsatile compliance evaluation. The overview of venous reactivity greatly differs, being poorly studied in vivo, mainly by optical methods in humans or US echotracking in animals. Existing methodologies are potent but could be certainly developed and improved further for better characterization of the SV in human and for investigations of new devices, surgical techniques and pharmacological treatment in preclinical animal studies.

In vivo analysis of adrenergic and serotoninergic constrictions of the rabbit saphenous vein

We aimed to develop a model to study in vivo the rabbit saphenous vein pharmacology and to investigate constrictions mediated by adrenoceptor and 5-HT receptor subtypes. We used the technique of high precision ultrasonic echo-tracking for direct measurement of saphenous vein diameters in pentobarbital anesthetized rabbits. Saphenous vein constrictions induced in rabbits by the alpha(1)-adrenoceptor agonist L-phenylephrine and the 5-HT(1B) receptor agonist sumatriptan were comparable with those induced in dogs but those induced by the 5-HT(1B) and 5-HT(7) receptor agonist 5-carboxamidotryptamine failed to appear in dogs. Dose-related constrictions of rabbit veins were obtained with L-phenylephrine and the alpha(2)-adrenoceptor agonist dexmedetomidine. Frequency-related constrictions of rabbit veins induced by nerve stimulation were partially inhibited by an alpha(1)-adrenoceptor or a postsynaptic alpha(2)-adrenoceptor antagonist (prazosin and SKF 104,078) but not affected by the pre- and post-synaptic alpha(2)-adrenoceptor antagonists BRL 44408 or rauwolscine. Constrictions of rabbit veins to sumatriptan and 5-CT were inhibited by GR 127935 and those induced by quipazine, a 5-HT(2) receptor agonist were prevented by ritanserin. The initial constrictions induced by 5-CT were followed by dilatations which were inhibited by the 5-HT(7) receptor antagonist mesulergine. These data indicate that rabbit saphenous veins, in vivo and at rest, respond to activation of 5-HT(1B) and 5-HT(2) receptors, alpha(1)- and alpha(2)-adrenoceptors and nerve stimulation; the dilator effect mediated by 5-HT(7) receptor activation was also detected. The data validate a new animal model to study superficial vein reactivity and its pharmacological sensitivity.

Recording of the saphenous vein compliance by an ultrasonic echo-tracking device in the dog: effects of S 18149

1. Saphenous vein reactivity was recorded in the anaesthetized dog by use of an ultrasonic echo-tracking device to measure the internal diameter of the vein and to calculate the venous compliance. This method was used to investigate the effects of a new partial alpha1/alpha2-adrenoceptor agonist, S 18149, on the canine saphenous vein in vivo after intravenous (i.v.) or oral administration. 2. Venoconstrictions induced by i.v. or local administration of compounds were evaluated by continuous recording of the internal diameter of the saphenous vein with the echo-tracking method. Venous compliance was calculated in two ways: (1) as the slope of the diameter-pressure curve obtained by increasing the venous pressure with an inflatable cuff and (2) in veins in which pressure was higher than 12 mmHg, pulsatile variations in the venous diameter and venous pressure were detected and used to calculate the pulsatile compliance of the vein. 3. S 18149 administered i.v. at 0.5 microg kg(-1) min(-1) for 10 min induced a decrease in the saphenous vein diameter (-15+/-3%) and blood flow (-72+/-6%) associated with an increase in saphenous vein resistance; at the dose used, S 18149 did not modify venous pressure and caused only a weak increase in arterial pressure (+7+/-2 mmHg). 4. The pulsatile compliance of the saphenous vein averaged 8.65+/-1.37 mm2 x 100 mmHg(-1) in control dogs and was significantly decreased to 5.13+/-0.68 mm2 x 100 mmHg(-1) in the same animals after treatment with S 18149 at 100 microg kg(-1) per os (n=10). The saphenous vein compliance calculated with the increased external pressure method averaged 24.90+/-1.49 microm mmHg(-1) in control dogs and was significantly reduced in the same animals after treatment with S 18149 at 100 microg kg(-1) per os to 9.06+/-3.42 microm mmHg(-1) (n=5). When constrictions of the vein were induced with increasing doses of (-)-phenylephrine, injected locally at 1, 3 or 6 microg min(-1), only the responses obtained with the lower dose of (-)-phenylephrine were increased in dogs treated with S 18149 100 microg kg(-1) per os (-16+/-4% versus -4+/-3%, n=5). 5. These results show that the high resolution echo-tracking device previously used for arterial compliance measurements, allows the detection of pulsatile changes in the canine saphenous vein and thus permits calculation of both the pulsatile and the static compliance of superficial veins in vivo. Using this technique, we have demonstrated that the novel alpha-adrenoceptor agonist S 18149 constricts the canine saphenous vein in vivo and decreases the saphenous vein compliance after oral administration.

In Vivo Compliance of the Human Saphenous Vein Measured by Sonography: Comparison with Plethysmographic and in vitro Measurements

Objective:

To evaluate a non-invasive and selective measurement of in vivo venous compliance of the human saphenous vein using sonography.

Design:

An experimental study in patients prior to coronary bypass surgery.

Setting:

Departments of Physiology and Cardiothoracic Surgery, University Hospital of Angers.

Patients:

Thirty patients investigated prior to coronary bypass surgery.

Interventions:

Simultaneous strain-gauge venous occlusion plethysmography (VOP) and measurements of the circumference of the great saphenous vein by sonography at four different occlusion pressures: 20, 30, 40 and 50 mmHg. In 10 of the same patients, in vitro determination of pressure–volume relationship during progressive inflation of excised saphenous vein samples.

Main outcome measures:

Venous compliance obtained with the three methods.

Results:

Weak correlation coefficients were found between in vitro measurements and VOP ( r=0.478, p<0.01) and sonography ( r=0.497, p<0.02). Although individual correlations between in vitro and VOP measurements ranged from 0.928 to 0.999, a wide heterogeneity was found with sonography (from 0.620 to 0.985).

Conclusions:

Sonography allows the selective measurement of in vivo venous compliance, although the measured compliances differ from other techniques.

Venoconstrictor responses to dihydroergocristine and dihydroergotamine: evidence for the involvement of 5-HT1 like receptors

Dihydroergocristine (DHEC) and dihydroergotamine (DHE) were investigated on canine saphenous veins in vivo and on canine saphenous veins and basilar arteries in vitro. Following local i.v. infusion in vivo, the venoconstrictor response to DHEC was about 30% weaker than that produced by DHE. When administered orally, however, both ergot alkaloids elicited similar venoconstrictor effects. In vitro maximal contractile responses to DHEC and DHE of basilar arteries were only 20-30% of those produced by 5-HT, whereas in saphenous veins both DHEC and DHE elicited similar maximal effects as those observed with 5-HT. In saphenous veins, methiothepin antagonized venoconstrictor responses to 5-HT, DHEC, and DHE within the same concentration range, being significantly less potent when tested against noradrenaline. The reverse was true for yohimbine, which was significantly more potent against noradrenaline than against 5-HT, DHEC, and DHE. It is suggested that the venoconstrictor responses to both DHEC and DHE are mediated through 5-HT1-like receptors.

Interaction of cyclosporine-A with the renin-angiotensin system in canine veins

Responses of canine saphenous veins to bradykinin and angiotensin and the effect of cyclosporine-A were investigated both in conscious dogs in vivo and on ring preparations from canine saphenous veins in vitro. In vivo local infusion of bradykinin into the saphenous vein elicited dose-dependent reduction in compliance, i.e., venoconstriction, whereas local infusion of angiotensin elicited dose-dependent venodilatation, which was markedly enhanced during blockade of endogenous thromboxane A2 synthesis by dazoxiben (2.5 mg/kg i.v.). The venoconstrictor response to bradykinin was attenuated after oral administration of both the thiazide-like diuretic clopamide (0.5 mg/kg) or cyclosporine-A (30 mg/kg), and by concomitant local infusion of cyclosporine-A (1-10 micrograms/min). Systemic i.v. infusion of the renin inhibitor H-77 (0.1 mg/kg/h) reversed the inhibition of bradykinin by both clopamide and cyclosporine-A. In vitro bradykinin elicited relaxation at low (0.1-10 nmol/l) but constriction at higher concentrations. The venoconstrictor response to bradykinin was resistant to blockade of thromboxane A2 synthesis and only partially attenuated after selective blockade of cyclooxygenase or lipoxygenase. Concomitant blockade of both lipoxygenase and cyclooxygenase activity by nordihydroguaiaretic acid (NDGA 10-30 mumol/l) nearly abolished the contractile response thereby enhancing the relaxant component of the bradykinin effect. Angiotensin II also elicited biphasic responses of partially contracted venous rings. Concomitant blockade of both lipoxygenase and cyclooxygenase by NDGA (10 mumol/l) again attenuated the contractile component of the angiotensin effect thereby unmasking the venodilator activity which could be inhibited by the angiotensin II receptor blocker saralasin (0.01-1 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the venous compliance by bradykinin and angiotensin II and its significance for the vascular effects of cyclosporine-A

Local infusion of both bradykinin and enalaprilic acid, the active metabolite of the converting enzyme inhibitor enalapril, elicited dose-dependent reduction of the compliance of the saphenous vein in conscious dogs. The competitive bradykinin B1-receptor antagonist, des-Arg9-Leu8-bradykinin antagonized venous responses to both bradykinin and enalaprilic acid effectively and with similar potency whereas the bradykinin B2-receptor antagonist Thi5,8,D-Phe7-bradykinin was about 100 times less potent when tested against bradykinin. Under control conditions local infusion of angiotensin II had no contractile activity but it elicited considerable venodilation after blockade of endogenous thromboxane A2 synthesis by dazoxiben. Blockade of the converting enzyme by enalapril (3 mg/kg i.v.) enhanced the maximal responses to bradykinin. Under these conditions concomitant local infusion of angiotensin II attenuated the venoconstrictor effects of bradykinin. Venous responses to bradykinin were inhibited after oral treatment of the dogs with the thromboxane A2 receptor antagonist BM 13,177 and nearly completely abolished after i.v. administration of the thromboxane synthesis inhibitor dazoxiben. In contrast, venous responses to enalaprilic acid were unchanged by thromboxane A2 receptor blockade and enhanced after dazoxiben. Following oral administration of cyclosporine-A (10 and 30 mg/kg), venous responses to bradykinin were attenuated while those to enalaprilic acid remained unchanged. Concomitant local infusion of the angiotensin II receptor antagonist saralasin (1 microgram/min) reversed completely the cyclosporine-A-induced reduction of the venoconstrictor effects of bradykinin.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of nitroglycerin on exercise-induced regional myocardial contractile dysfunction are not diminished by pretreatment with dihydroergotamine

1 Because controversy exists regarding the effects of dihydroergotamine (DHE) on the performance of underperfused myocardium, the effects of DHE were investigated in a model of exercise-induced regional myocardial dysfunction in conscious dogs. 2 We also investigated a possible functional antagonism between DHE and nitroglycerin that might reduce the latter drug's antianginal efficacy. 3 Investigations were carried out in conscious dogs. After stenosis of the circumflex branch of the left coronary artery that minimally affected resting myocardial function, treadmill exercise induced transient regional contractile dysfunction. Heart rate, arterial blood pressure, left ventricular dp/dtmax and left ventricular end-diastolic pressure were registered. Regional contractile performance was assessed by ultrasonic distance measurement in the underperfused and in a normally perfused area. 4 DHE (5 micrograms kg-1, i.v.) induced a decrease in left ventricular dp/dtmax at rest and during exercise. DHE did not cause a deterioration in contractile function in the ischaemic myocardium, but led to a slight although not significant improvement in regional myocardial function. 5 After pretreatment with DHE, infusion of nitroglycerin (15 micrograms kg-1, i.v.) induced an improvement in the underperfused myocardial area during treadmill exercise, accompanied by a decrease in diastolic arterial pressure and left ventricular end-diastolic pressure and an increase in left ventricular dp/dtmax. 6 These results suggest that DHE will not worsen exercise-induced angina pectoris, and that the antianginal efficacy of nitroglycerin will not be neutralized by pretreatment with DHE.

Methylergometrine, an active metabolite of methysergide

In conscious dogs methysergide (MS) caused constriction of the saphenous vein at about 3000 times lower doses than methylergometrine (MT) when infused locally, but it elicited only a short-lasting venoconstrictor response when injected systemically intravenously. MS and MT proved to be equally active venoconstrictor agents when administered orally. Analysis of canine plasma by high-performance liquid chromatography showed that after both oral and intravenous administration of MS large amounts of MT appeared in the plasma, whereas only low and transient levels of MS could be detected. It is suggested that one of the first steps in metabolism of MS is demethylation at position 1 of the indole, leading to the formation of MT, which may be a main active principle of the therapeutic effectiveness of MS in the interval treatment of migraine headache.