Smokers have severely disturbed peripheral micro-circulation.

AIM: The aim of this study was to determine the effect of smoking a single cigarette on the blood flow rates in capillaries and arteriovenous anastomoses (AVAs) in light and heavy smokers in: a) the skin fold between the first and second fingers, and b) the pulp of the thumb. METHODS: Five light (10-12 cigarettes/day) and 5 heavy (>20 cigarettes/day) chronic smokers participated (4 men and 6 women, median age 40.5 years). The blood flow rates were measured by the (133)Xenon local washout method (capillaries, skin fold) and the heat washout method (AVAs, thumb pulp), respectively, before, during, and after smoking of a single Prince cigarette (0.9 mg nicotine). RESULTS: The blood flow rate (f) in mL(100 g(min)(-1) [standard error, SE] in skin capillaries of light smokers was 24.4 [9], 8.9 [1.8], and 10.4 [3.3] before, during, and after smoking of one cigarette; in heavy smokers, f was 23.6 [10.9], 16.1 [5.3], and 7.1 [2.9]; f in pulp AVAs of light smokers was 130.6 [14.9], 49.2 [24.8], and 119.7 [20.9] before, during, and after smoking; in heavy smokers, the corresponding results were 134.4 [19.1], 136.2 [13.5], and 143 [15.3]. Thus, the blood flow rate in capillaries of both light and heavy smokers was higher before smoking the test cigarette than previously observed in non-smokers. In light smokers blood flow rate in AVAs decreased during smoking with a factor of 2.6, and it returned to the pre-smoking level immediately after the end of smoking the cigarette. In heavy smokers, f remained unchanged before, during, and after smoking. CONCLUSIONS: Smokers have severely disturbed peripheral microcirculation.

Thoracic sympatholysis with epidural blockade assessed by quantitative measurement of cutaneous blood flow.

BACKGROUND: Quantifying sympathetic activity is difficult. Direct measurement is possible and superior to indirect techniques, but nerves to internal organs are not accessible in humans. Recently, we validated a quantitative technique for measurement of cutaneous blood flow using heat as an indicator. The aim of the study was to investigate whether sympatholysis during thoracic epidural blockade (TEA) may be documented by changes in regional cutaneous blood flow. A secondary aim was to assess whether, during TEA, local heating itself enhances regional blood flow. METHODS: Six patients scheduled for elective coronary artery bypass grafting (CABG) were studied. An epidural catheter was inserted at the T2-3 interspace. Measurements were performed with an electrode, which can measure the local temperature of the skin. The probe is covered with a thermostatically controlled cap to avoid a thermic gradient to air. As a result of the cap, a change in temperature of the central disc depends almost solely on the blood flow in the underlying tissue. Regional cutaneous blood flow rates were measured before and after epidural anesthesia with and without local heating. RESULTS AND COMMENTS: All patients had a sensory blockade covering at least T1-5. Cutaneous blood flow increased in all six patients after blockade (13.6 ml/min/100 g, range 10.6-14.6 vs. 18.4 ml/min/100 g, range 13.9-24.5; P<0.05). Local heating did not further enhance blood flow. CONCLUSION: High TEA is associated with a uniform increase in thoracic cutaneous blood flow, and is suggestive of regional sympatholysis. Quantitative measurements of skin blood flow appear promising for documenting regional sympatholysis during TEA.

Is non-specific aneurysmal disease of the infrarenal aorta also a peripheral microvascular disease?

OBJECTIVES: to examine whether aneurysmal disease of the aorta has a functional component in the peripheral microIvasculature. MATERIALS: ten normal persons; and 15 patients who had been operated on for ruptured non-specific infrarenal aortic aneurysm months to years previously were studied. METHODS: blood flow rates were measured: (a) in the subcutaneous adipose tissue of the forefoot by the(133)xenon local washout method (perfusion through nutritive capillaries supplied by arterioles with elastin in the tunica media); and (b) in the arteriovenous anastomoses of the pulp of the first toe as measured by the heat washout method (perfusion predominantly through thick-walled tubes without elastin). Perfusion rates were measured in supine subjects at heart level, at 30 cm above and at 30 cm below heart level. RESULTS: in subcutaneous adipose tissue, the capillary blood flow rate was four times higher in patients with aneurysmal disease than in normal subjects. Both groups exhibited autoregulation of blood flow and a normal veno-arteriolar sympathetic axon reflex. Blood flow rates in the arteriovenous anastomoses of the pulp did not differ between aneurysm patients and normal subjects. Autoregulation and the axon reflex were absent in the arteriovenous anastomoses of normal subjects as well as in aneurysm patients. CONCLUSIONS: non-specific aneurysmal disease of the infrarenal aorta has a peripheral functional component affecting arterioles but not arteriovenous anastomoses.

Peripheral blood flow rates and microvascular responses to orthostatic pressure changes in claudicants before and after revascularisation.

OBJECTIVES: To study the effect of arterial reconstruction for occlusive atherosclerotic disease with intermittent claudication on blood flow rate during rest and on microvascular responses to orthostatic pressure changes in the pulp skin of the first toe where arteriovenous anastomoses are numerous. MATERIAL: Eleven patients with Fontaine IIa claudication (ankle blood pressure index > 0.30) before and 7 (range: 2-11) months after intervention. METHODS: Blood flow rate was measured by the heat washout method with the toe at heart level and after passive lowering to 50 cm below this level using a Clark type electrode with thermostatically controlled cap that was fixed to the pulp of the first toe by adhesive tape. RESULTS: At heart level, blood flow rate was lower in claudicants before reconstruction as compared to a group of previously published control subjects (p = 0.0076, Wilcoxon), blood flow rate increased in claudicants from before to after intervention (p = 0.0128), and postoperative blood flow rate was like that of normals (N.S.). Before surgery, blood flow rate in claudicants increased in median with a factor of 1.79 during lowering (p < 0.0051). CONCLUSIONS: The disturbance of the microcirculatory responses to orthostatically induced pressure changes in claudicants reverted towards normal after arterial reconstruction.

Isokinetic eccentric exercise as a model to induce and reproduce pathophysiological alterations related to delayed onset muscle soreness.

Physiological alterations following unaccustomed eccentric exercise in an isokinetic dynamometer of the right m. quadriceps until exhaustion were studied, in order to create a model in which the physiological responses to physiotherapy could be measured. In experiment I (exp. I), seven selected parameters were measured bilaterally in 7 healthy subjects at day 0 as a control value. Then after a standardized bout of eccentric exercise the same parameters were measured daily for the following 7 d (test values). The measured parameters were: the ratio of phosphocreatine to inorganic phosphate (PCr/Pi), the ratio of inorganic phosphate to adenosintriphosphate (Pi/ATP), the ratio of phosphocreatine to adenosintriphosphate (PCr/ATP) (all three ratios measured with 31P-nuclear magnetic resonance spectroscopy), dynamic muscle strength, plasma creatine kinase (CK), degree of pain and "muscle" blood flow rate (133Xenon washout technique). This was repeated in experiment II (exp. II) 6-12 months later in order to study reproducibility. In experiment III (exp. III), the normal fluctuations over 8 d of the seven parameters were measured, without intervention with eccentric exercise in 6 other subjects. All subjects experienced pain, reaching a maximum 48 h after eccentric exercise in both exp. I and II. A systematic effect over time for CK (increasing 278% resp. 308%), muscle strength (decreasing more than 10%), PCr/Pi (decreasing 31% resp. 43%) and Pi/ATP (increasing 55% resp. 99%) was found in both exp. I and II (P < 0.05), but not in exp. III. No significant difference was observed between exp. I and II for CK, blood-flow rate, concentric muscle strength, PCr/Pi, Pi/ATP and PCr/ATP. It is concluded that pathophysiological alterations in m. quadriceps following eccentric exercise can be induced and can be reproduced after an interval of 6 months. Thus, this model can be used to study the effects of physiotherapy.

The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise.

The aim of this study was to measure if passive stretching would influence delayed onset muscle soreness (DOMS), dynamic muscle strength, plasma creatine kinase concentration (CK) and the ratio of phosphocreatine to inorganic phosphate (PCr/P(i)) following eccentric exercise. Seven healthy untrained women, 28-46 years old, performed eccentric exercise with the right m. quadriceps in an isokinetic dynamometer (Biodex, angle velocity: 60 degrees.s-1) until exhaustion, in two different experiments, with an interval of 13-23 months. In both experiments the PCr/P(i) ratio, dynamic muscle strength, CK and muscle pain were measured before the eccentric exercise (day 0) and the following 7 d. In the second experiment daily passive stretching (3 times of 30 s duration, with a pause of 30 s in between) of m. quadriceps was included in the protocol. The stretching was performed before and immediately after the eccentric exercise at day 0, and before measurements of the dependent variables daily for the following 7 d. The eccentric exercise alone led to significant decreases in PCr/P(i) ratio (P < 0.001) and muscle strength (P < 0.001), and an increase in CK concentration (P < 0.01). All subjects reported pain in the right m. quadriceps with a peak 48 h after exercise. There was no difference in the reported variables between experiments one and two. It is concluded that passive stretching did not have any significant influence on increased plasma-CK, muscle pain, muscle strength and the PCr/P(i) ratio, indicating that passive stretching after eccentric exercise cannot prevent secondary pathological alterations.

Cutaneous blood flow rate in areas with and without arteriovenous anastomoses during exercise.

In 10 healthy subjects, skin blood flow rate was measured in the thumb pulp by the heat-washout method, and in the skin fold between the thumb and the forefinger by the 133Xe-washout method. The former but not the latter skin area contains arteriovenous anastomoses (AVAs). In response to 10 min moderate bicycle exercise, an instantaneous decrease in flow was seen in the thumb pulp followed after about 4.6 min by an increase to resting levels. Blood flow in the skin fold remained constant. The results indicate that the initial reduction in blood flow rate and later increase observed in the finger at the onset of moderate exercise take place in the AVAs and not in the capillaries.

Blood flow rate during orthostatic pressure changes in the pulp skin of the first toe.

OBJECTIVES: Determination of the local regulation of cutaneous blood flow through nutritive capillaries and through arteriovenous anastomoses of the pulp of the first toe in response to passively induced orthostatic blood pressure changes in normal subjects and in patients with occlusive atherosclerotic disease. MATERIAL: Six normal subjects, seven patients with unilateral, crural intermittent claudication and six patients with unilateral, chronic critical ischaemia. METHODS: Blood flow rates were measured in supine subjects by the heat washout method (the sum of blood flow rate in arteriovenous anastomoses and blood flow rate in nutritive capillaries) and by the 133Xenon washout method (blood flow rate in nutritive capillaries) after local, atraumatic labelling. Measurements were made with (a) the toe passively elevated to 50 cm above heart level, (b) at heart level and (c) passively lowered to 50 cm below heart level. RESULTS: Autoregulation of nutritive blood flow was present in normal subjects and in claudicants, but the local sympathetic veno-arteriolar axon reflex was absent in both groups. In patients with critical ischaemia blood flow rate was the same in the supine position and during lowering in arteriovenous anastomoses and in nutritive capillaries. The arteriovenous anastomoses had distinct and characteristic reaction patterns in response to lowering in each of the three examined groups and to elevation in normal subjects and in patients with intermittent claudication (not measured in patients with critical ischaemia). CONCLUSIONS: The microvascular responses to changes of orthostatic blood pressure differed among the three groups (normal subjects, patients with intermittent claudication, patients with critical chronic leg ischaemia). The heat washout method may be used to detect the functional significance of occlusive atherosclerotic disease.

Diffusional transport of the aminoterminal propeptide of type III procollagen in the interstitium of the globally ischaemic cat myocardium.

Local repair after acute myocardial infarction appears to be reflected by levels in serum of the aminoterminal propeptide of type III procollagen (serum-PIIINP). Furthermore, serum-PIIINP has recently been reported to provide information on prognosis after acute myocardial infarction. However, no attention has yet been paid to the resistance to diffusion offered by the myocardial interstitium. We determined the diffusion coefficient of PIIINP in the interstitium of the globally ischaemic interstitium of the cat (D'37) by means of a "true transient diffusion' method, and compared with the free diffusion in water (D37). D'37 (in cm2 s-1.10(-5) was 0.0157 +/- 0.0005 (mean +/- SEM) (n = 13), and D37 was 0.0624 +/- 0.0024 (n = 12). The mean diffusive progression during 20 min of the concentration profile of [125I]PIIINP into the tissue was calculated to be 0.19 mm. The D'37 of albumin is practically identical to the D'37 of PIIINP, and the myocardium offers a similar resistance to diffusion of PIIINP and albumin, as expressed from the ratio D37/D'37 of approximately 4 for both molecules. PIIINP has a molecular weight of 42,000 Da, is rod shaped and has an overall negative charge. These characteristics explain the similarity in diffusion coefficients of PIIINP and albumin, which has a molecular weight of 69,000 Da. Albumin is known to pass the membrane of the continuous capillaries of the heart, making it very likely that direct exchange of PIIINP between interstitium and capillary plasma can also occur. During one hour of interstitial diffusion PIIINP will have traversed a distance calculated tp correspond to 15-20 capillaries. Therefore, the results support the concept of serum-PIIINP as a direct marker of events taking place locally in the myocardium following acute myocardial infarction.

Heat-washout: a new method for measuring cutaneous blood flow rate in areas with and without arteriovenous anastomoses.

A new method, the heat-washout method, for measuring total cutaneous blood flow rate is introduced. The measurements were performed with a transcutaneous (tc) PO2-electrode that is capable of heating and measuring local temperature, and it is constructed with a thermostatically controlled cap. The probe was heated electrically to a selected temperature 2-10 degrees above normal skin temperature. When the temperature was stable, the heating element was turned off, and the temperature was registered every 10 s until a stable baseline temperature, Tb, was obtained. Tb was subtracted from the registered temperatures giving deltaTs that were plotted in a semilogarithmic diagram. The heat-washout was monoexponential, and the slope was used for calculating blood flow rate in accordance with the principle of Kety, using a known partition coefficient. The method was applied to the forearm in two subjects, and the results were compared to blood flow rates obtained simultaneously by the 133Xe-washout method in the same area. The equation of the regression line was y = 2.5 + 0 x 968X and the correlation coefficient was 0 x 986 at temperature levels of 37-45 degrees C. In the pulp of the thumb, blood flow rates, in arteriovenous anastomoses, were estimated in two subjects by subtracting the capillary blood flow rate, measured by 133Xe-washout, from the total cutaneous blood flow rate, measured by heat-washout. Due to a relatively low diffusions coefficient for 133Xe compared to heat, 133Xe cannot be used for measurement of blood flow rate in arteriovenous anastomoses.

Blood flow rate in arteriovenous anastomoses and capillaries in thumb, first toe, ear lobe, and nose.

Measurements of blood flow rate in the pulp of the thumb, the first toe, the ear lobe, and the nose were performed using the heat-washout method, and the 133Xe-washout method under orthostatic changes in humans. Blood flow rate measured by the heat-washout method in the thumb was about 127.5 ml (100 g x min)-1 at heart level in two subjects, (n=10), and in the pulp of the first toe in 6 subjects (n=12) 49.3 ml (100 g x min)-1 at heart level. Above heart level blood flow rate decreased with the falling pressure head, and 50 cm below heart level blood flow remained unchanged compared to heart level. The arterioles supplying the capillaries in this region showed autoregulation of blood flow to 50 cm above heart level, but a veno-arteriolar reflex was not present. Blood flow rate in the ear lobe and on the side of the nose showed a similar pattern of reaction, with a blood flow rate in the arteriovenous anastomoses of about 100 ml (100 g x min)-1 in sitting position.

Microvascular function in the peripheral vascular bed during ischaemia and oxygen-free perfusion.

OBJECTIVES: To determine the influence of acute ischaemia and absence of leukocytes on the microvascular function and capillary permeability in skeletal muscle. DESIGN: Prospective, open study. SETTING: University Department of Vascular Surgery and Institute of Medical Physiology. MATERIALS AND METHODS: Ten isolated cat gastrocnemius muscles were perfused with oxygen-free Ringer-albumin solution through the femoral artery. At 5 microliters bolus with 14.8 MBq 51Cr-EDTA was injected through a side branch into the femoral artery, and the response function was detected over the muscle by a scintillation detector connected to a spectrometer and a computer. The perfusion coefficient was measured directly at the venous outlet. The response function was analysed in accordance with non-compartmental black box kinetic principles to give perfusion rate, capillary extraction fraction and capillary diffusional permeability-surface area product (PdS). In separate experiments the molecular size and the free diffusion coefficient of 51Cr-EDTA in water at 37 degrees C were determined by a modified true transient diffusion method. MAIN RESULTS: During perfusion the PdS-product increased as a function of flow rate, f, in accordance with the linear regression line PdS = 1.78 + 0.15 f between 5 to 60 ml/100 g/min. This permeative conductance was identical to that found previously in a similar experimental set up with oxygenated whole blood perfusion. During oxygen free perfusion the perfusion rate was a linear function of arterial perfusion pressure, and autoregulation of blood flow did not occur in response to variations of arterial perfusion pressures. The free diffusion coefficient in water at 37 degrees C for 51Cr-EDTA was 7.4 x 10(-6) cm2/s (n = 36), which corresponds to a Stokes-Einstein molecular radius, rSE, of 0.439 nm. CONCLUSIONS: In spite of complete anoxia and absence of normal microcirculatory flow regulating mechanisms there is no sign of changes in capillary diffusional permeability for smaller hydrophilic molecules and functional membrane damage is not elicited in the absence of oxygen under these conditions.

A semiconductor silicon PIN diode matrix detector for measurement of 133Xe washout in small regional skin areas.

Local variations in microvascularization are expected in lesions and lesion-free skin of patients with pressure sores. To investigate these variations, methods for studies of the regional blood flow rate within small skin areas are needed. Regional blood flow can be estimated by measuring the washout of 133Xe from the tissue. This study describes a 2 x 12 Si PIN diode matrix detector capable of 133Xe detection, and equipped with a collimator to improve the spatial resolution. Thus the regional blood flow in subcutaneous skin areas down to about 2 cm2 can be investigated when the atraumatic epicutaneous labelling technique is used. The capability of the matrix detector and its collimator is described by laboratory investigations. In pilot investigations three normal subjects and three paraplegics with pressure sores were studied. In each individual study the detector matrix was divided into six square areas containing four diode detectors each. Thus six 133Xe disappearance rate constants from adjacent subcutaneous tissue could be determined simultaneously.

A miniature silicon diode matrix detector for in vivo measurement of 133Xe disappearance following local tissue injection.

A variety of biological processes can be studied from the washout of compounds labelled with a gamma emitter. Conventional systems for measurement of gamma radiation can detect count rates at both the low and high energy range of the indicator in question, 133Xe. However, silicon (Si) photodiodes have the capability of measuring the lowest energies (25-40 keV) of gamma and x-ray emitters with sufficient efficiency when applied on the skin surface and close to the indicator depot. The purpose of the present study was firstly to evaluate a portable Si photodiode matrix detector system, composed of 16 photodiodes, for in vivo measurement of disappearance rate constants of 133Xe following injection into subcutaneous (SC) or skeletal muscle (SM) tissues as compared with a stationary sodium iodide single crystal detector. Secondly, from these results, to evaluate the contribution from intra-tissue indicator diffusion and indicate means of avoiding influence from local diffusion in the washout curve of 133Xe. From the recorded 133Xe distribution in the depot proper, Si photodiodes in the matrix were selected for calculation of the washout. The Si matrix detector was reliable with a constant linearity and sensitivity within the range 20-38 degrees C and calibrated to +/- 1% between diodes. The in vivo investigations comprised two SC injections on humans with four measuring periods for comparison, and four SC and five SM injections on dogs, resulting in eight and five measuring periods for comparison. Only when the results obtained from the Si photodiodes at the position just above the count rate maximum were selected, was the contribution from diffusion significant. The ability to detect geometry changes is advantageous in studies with potential motion artefacts, such as during exercise.

Transport of beta-blockers and calcium antagonists by diffusion in cat myocardium.

Beta-blockers and calcium antagonists have been claimed to possess cardioprotective properties. This study addresses the question of whether a significant amount of these drugs will reach the cardiac myocytes during no-flow ischemia, where solute transport depends solely on diffusion. In anesthetized cats the hearts were excised. Apparent diffusion coefficients in cat myocardium at 37 degrees C (D'37) for 14C-verapamil (protein bound), 3H-metoprolol (lipophilic), 3H-atenolol (hydrophilic), and 3H-propranolol (lipophilic and protein bound) were determined by means of a "true transient diffusion" method and compared with the free diffusion coefficients in water (D37). D'37 of 14C-verapamil, 3H-metoprolol, 3H-atenolol, and 3H-propranolol (in cm2 s-1 10(5)) were (mean +/- SEM) 0.025 +/- 0.002, 0.055 +/- 0.003, 0.041 +/- 0.007, and 0.025 +/- 0.002, respectively. The mean diffusive progression of the concentration profile of 3H-metoprolol and 3H-atenolol into the tissue during 20 min was calculated to be 0.36 and 0.31 mm, respectively. The protein binding of 14C-verapamil and 3H-propranolol caused a significant fall in the progression to 0.24 mm for both drugs. These results indicate that, by diffusion, these drugs traverse the tissue too slowly to reach a significant amount of myocardium before myocyte necrosis occurs during conditions of noflow. Cardioprotective drugs are probably most effective, provided sufficient amounts are present in the tissue prior to the ischemic episode or sufficient supply via collateral blood flow is achieved.

Measurement of capillary permeability in canine heart determined by the tissue injection, residue detection method.

In previous studies the tissue injection, residue detection method failed to provide results of diffusional capillary permeability comparable to those of other methods. For this reason we reconsidered the kinetic theory and found that it is necessary to take into account the apparent (restricted) diffusion coefficient of the indicator within the tissue, D', in order to determine the permeability-surface area product, PdS = Vev.D.D'-1.tev-1 = Vev'.klo where D is the diffusion coefficient in free aqueous solution, Vev is the physical interstitial water volume of distribution, Vev' is the virtual (apparent) interstitial volume of distribution, tev is the mean transit time of the indicator, and klo is the recorded fractional initial washout rate constant. In experiments on open chest dog hearts we examined capillary permeability for 51Cr-EDTA and 99mTc-DTPA with the tissue injection, residue detection method and the single injection, residue detection method. Blood flow was measured independently with local 133Xenon washout. D and D' were measured by a true transient diffusion method. We found that the tissue injection, residue detection method gave results for capillary extraction and PdS-product similar to those obtained with a number of other methods based on indicator diffusion, so the tissue injection, residue detection method in its new kinetically correct formulation could prove useful in clinical studies of capillary permeability since it is applicable to determination of relative changes of permeability during interventional procedures.

Effects of neuropeptide Y on regulation of blood flow rate in canine myocardium.

The effect of neuropeptide Y (NPY) on tension development was examined in isolated canine coronary arteries, and the effects on local myocardial blood flow rate were studied in open-chest anesthetized dogs by the local 133Xe washout technique. By immunohistochemistry, numerous NPY-like immunoreactive nerve fibers were identified in the adventitia of canine coronary arteries. NPY (10(-9)-10(-6) M) supplied to isolated epicardial segments of the left anterior descending coronary artery induced a modest vasoconstriction, with a maximum tension of 0.95 mN, that was only 6.9% of the response to K+. In contrast, intracoronary NPY (0.01-10 micrograms) induced a considerable degree of vasoconstriction; the reduction of blood flow rate was dose related, with a maximum reduction to 52% of control values. The effect of intracoronary NPY (1 microgram) on maximally relaxed arterioles elicited by 30 s of ischemia was studied in separate experiments during reactive hyperemia. NPY induced a decrease in maximum blood flow during reactive hyperemia (166.6 vs. 214.6% of preocclusive blood flow rate, mean values; P = 0.05), an increase in the cumulative excess blood flow (61.0 vs. 35.3 ml/100 g; P = 0.02), and an increase in the duration of reactive hyperemia compared with control values (66 vs. 41 s; P = 0.02). Thus we conclude that in the heart NPY is a potent vasoconstrictor that seems to act preferentially on smaller intramyocardial arterioles. Furthermore, NPY inhibits vascular relaxation of myocardial resistance vessels after ischemia, suggesting that this peptide may participate in the regulation of myocardial blood flow not only during physiological conditions but also after ischemia.

Capillary permeability of 131I-albumin in the resting human forearm.

STUDY OBJECTIVE: The aim was to examine capillary permeability of 131I-albumin in the normal, resting human forearm. DESIGN: A bolus injection of 131I-albumin was injected into the brachial artery, and the residue function was measured by external registration over the forearm tissues. The results were analysed by indicator kinetic "black box" theory using the single injection, residue detection method which is based on indicator diffusion principles. SUBJECTS: Seven normal volunteers participated in the study. MEASUREMENTS AND MAIN RESULTS: The mean capillary extraction fraction of 131I-albumin was 0.023 (SD 0.0056), n = 7, at a mean plasma flow rate of 2.1 (0.34) ml.100 g-1.min-1. At an estimated capillary surface area of 70 cm.g-1 the permeability coefficient was 11.10(-8) cm.s-1. CONCLUSIONS: According to the theories of restricted diffusion and equivalent pores the results are compatible with an equivalent pore radius estimate of 113 A using additional previously published results from experiments with 51Cr-EDTA.

Mucosal/submucosal blood flow in the small intestine in pigs determined by local washout of 133Xe and microsphere techniques.

In 11 anaesthetized pigs a laparotomy was performed and the mucosal and submucosal blood flow rate in the small intestine of the pig was determined by a local application of 133Xe and by 6.5-microns radioactive microspheres. The 133Xe washout plotted in a semilogarithmic diagram showed a multiexponential configuration. As localization studies of 133Xe in the intestinal mucosa showed a constant high concentration of 133Xe in the luminal part of the mucosa due to shunting by diffusion, the initial slope of the 133Xe washout was used for blood flow determination in the mucosa/submucosa. There was a good relationship between blood flow determined by the two techniques. The correlation coefficient, R, between the two techniques was 0.89.

Neuropeptide Y reduces ovarian blood flow in the rabbit.

Neuropeptide Y-containing nerve fibers have previously been demonstrated to innervate the mammalian ovary. These nerve fibers innervate primarily the vasculature. In this study we have developed a method for in vivo measurement of the ovary blood flow rate by means of the 133Xe method. Using this technique we measured the ovary blood flow rate and investigated the dose-response relationship between close intraarterial-injected NPY and the ovary blood flow rate. A monoexponential washout curve for 133Xe was found for the whole washout process, ensuring that the blood flow rate at any time could be calculated from the curve. We found a mean blood flow rate in the nonpregnant rabbit ovary at 43.6 +/- 4.4 ml.(100 g)-1.min-1 (mean +/- SEM). Injection of NPY (20, 200, 2000 pM) in the aorta close to a. ovarica resulted in a dose-dependent decrease in the ovarian blood flow rate with a maximum reduction to 40.7 +/- 6.3% (mean +/- SEM) of the control blood flow rate. These findings make it likely that receptors able to interact with NPY are present in the vasculature of the rabbit ovary.