Increase In Muscle Blood Flow Research Articles

Lactic acid infusion in dogs: effects of varying infusate pH.

This study had two purposes: 1) to determine the effects of varying the pH of lactic acid infusion solutions on the acid-base status of anesthetized dogs, and 2) to determine the effect of elevated blood lactate concentration on muscle lactate concentration. The experiments were performed on the in situ gastro cnemius-plantaris muscle group in 14 mongrel dogs. The infusions increased the arterial blood lactate concentration to 11.0 +/- 0.5 (SE) mM after 20 min. Above an infusate pH of 4.4, the arterial pH increased by 0.118-0.167 during infusion; the arterial pH was unchanged when the infusate pH was between 3.4 and 4.0; and the arterial pH decreased as infusate pH decreased below 3.0. The effect of lactic acid infusion on blood pH appears to be the result of two opposing effects: 1) an acidifying effect due to its weak acid properties, and 2) an alkalinizing effect due to the metabolism of sodium lactate. The estimated ratio between intracellular muscle lactate and venous plasma water lactate averaged 0.647 +/- 0.038, indicative of a substantial gradient between blood and muscle. The infusion produced a significant change from lactate output to lactate uptake by the muscles. The infusion also transiently increased muscle blood flow and oxygen uptake.

Vascular and metabolic effects of methylprednisolone and phenoxybenzamine during controlled hypotension in the dog.

The relationship between central haemodynamics and vascular and metabolic parameters in skeletal muscle was studied in dogs subjected to controlled haemorrhagic hypotension and treated with cumulative doses of methylprednisolone (4-32 mg x kg-1), (or saline in the control group), followed by phenoxybenzamine. There were no significant haemodynamic or metabolic changes between the groups during the injections of steroid or saline. The alpha-adrenergic receptor blockade caused, as found earlier, a pronounced vasodilation in the steroid group, which was parallelled by an increase in muscle blood flow in the same order of magnitude. There was no clearcut relationship between metabolic and vascular effects in the groups. Despite the significant difference in blood flow between the groups after phenoxybenzamine, only small and insignificant differences were seen in muscle metabolites, with the exception of muscle lactate which showed higher values in the steroid group. The study provides further evidence in support of the hypothesis that the haemodynamic effects of the combination of methylprednisolone and phenoxybenzamine are of neurogenic origin.

Control of reciprocal and non-reciprocal action of vagal and sympathetic efferents: study of centrally induced reactions.

The mechanism of control of reciprocal and non-reciprocal action between parasympathetic and sympathetic nerves was investigated. Simultaneous recordings were made from both vagal and sympathetic nerves innervating the heart of responses evoked by hypothalamic stimulation in chloralose-anesthetized dogs. Four patterns of responses could be elicited by repetitive stimulations of various sites within the hypothalamus: (1) A reciprocal pattern of cardiac vagal and sympathetic discharges accompanied by a rise in blood pressure, heart rate and a 2 to 8-fold increase in muscle blood flow. The vagal activity completely ceased, while sympathetic discharges were greatly augmented. These changes occurred quickly and often lasted throughout the stimulation, preventing baroreceptor reflex from breaking through. This pattern is similar to the cardiovascular component of the "defense reaction". (2) A reciprocal pattern of discharges accompanied by a depressor response and bradycardia; the vagal discharges increased while those of the sympathetic efferents decreased. (3) A non-reciprocal pattern of response in which activity of the two efferents increased. The blood pressure was elevated and heart rate decreased. (4) A non-reciprocal pattern of action of the two efferents in which discharges of both nerves were depressed; the blood pressure decreased and heart rate increased. Factors affecting these responses patterns were found to be: (a) secondarily occurring reflex responses due to baroreceptor activation or deactivation. These baroreceptor-related reactions always showed reciprocal changes between vagal and sympathetic nerve activity; (b) the level of tonic activity of the autonomic nerves, e.g. during a high level of tonic activity inhibitory action became less effective while the excitatory effect was greater. Thus central states maintaining influenced the pattern of reaction and the relationship between activity in these two efferent nerves. Single pulse stimulations of the hypothalamic regions from which different patterns were evoked, when stimulated repetitively, yielded patterns which were basically reciprocal and biphasic; in vagus efferents an inhibitory phase was followed by an excitation of tonic activity, while in sympathetic an excitation was followed by an inhibition. The degree and duration of these excitatory and inhibitory phases differed, depending on the site of stimulation, but only to a minor degree, and the basic pattern remained unchanged. The implication of these findings is that the hypothalamus can organized both reciprocal and non-reciprocal patterns of activity in the two autonomic limbs in response to varied afferent stimuli. Probably only subtle changes in the central states or influences on neurons of the autonomic system suffice to result in different response pattern. No pattern of response is fixed within the central control complex.

Dorsal root vasodilatation in cat skeletal muscle.

1. A study has been made, in the cat anaesthetized with chloralose, of the effects of antidromic stimulation of dorsal roots L6-S1 on the blood flow through the gastrocnemius muscle. 2. Stimulation of the peripheral ends of the ligated dorsal roots with current pulses of 0.3-0.5 msec duration and at intensities most effective in activating the smaller afferent fibres, for periods of 15-20 sec, produced a 50-60% increase in muscle vascular conductance which was slow in onset and long outlasted the stimulus. 3. This muscle vasodilatation could be evoked in the paralysed animal and was unaffected by guanethidine or atropine. It was, however, greatly reduced or even abolished by the prostaglandin synthetase inhibitors, indomethacin or acetylsalicylic acid, in doses which had no effect on the dilatation produced by a local injection of acetylcholine or the functional hyperaemia induced by muscle contraction. 4. It is concluded that activity in the smaller myelinated or unmyelinated afferent fibres of skeletal muscle produces an increase in muscle blood flow which is mediated, at least in part, by prostaglandins locally synthesized within the muscle.

Lumbar sympathectomy and blood flow in the lower extremity

Blood flow in the superficial femoral artery and skin and muscle blood flows in the lower leg were measured in twenty-two patients before and one month after lumbar sympathectomy. The following conclusions were drawn: 1. (1) Lumbar sympathectomy markedly improved blood flow in the superficial femoral artery and decreased peripheral resistance. No correlation was found between these hemodynamic changes and improvement in clinical manifestations. 2. (2) Lumbar sympathectomy for intermittent claudication increased blood flow in the superficial femoral artery and skin blood flow through a decrease in peripheral resistance, but it in no way altered the muscle blood flow. No significant difference was noted in the degree of increase of muscle blood flow between the group with improved claudication and the unchanged group, but the skin blood flow tended to increase more markedly in the improved group than in the unchanged group. The improvement in claudication caused by lumbar sympathectomy thus appears to be due to a factor other than increased muscle blood flow.

The Compliance of the Resistance Vessels in Skeletal Muscle of Hypertensive Patients

1. The compliance of the resistance vessels in the anterior tibial muscle was compared in normotensive and hypertensive subjects by measuring the increase in muscle blood flow produced by an increase in vascular transmural pressure. 2. The transmural pressure was increased by exposing the leg to a pressure of 50 mmHg below atmospheric pressure. Muscle blood flow was measured by means of the local 133xenon wash-out technique, and the measurement was performed during reactive hyperaemia to avoid reflex vasoconstriction when the transmural pressure was augmented. 3. At ambient pressure, muscle blood flows were equal in the two groups. However, when the subatmospheric pressure was applied the blood flow increased twice as much in the normotensive as in the hypertensive subjects. This suggested a smaller compliance of the resistance vessels in hypertensive subjects and supported the concept that there are structural changes of the resistance vessels in arterial hypertension. 4. In a small group of hypertensive patients who were well treated for two years, and had a normal blood pressure, the compliance was reduced to the same extent as in the untreated hypertensive patients, indicating that structural vascular changes are not readily reversible despite appropriate antihypertensive treatment.

Effect of circulating FFA on lactate production by skeletal muscle during stimulation

The present experiments were undertaken to study the effects of FFA on lactate production by skeletal muscle during stimulation. In the first group, dogs were anesthetized with sodium pentobarbital and given no anticoagulant. The second group was also anesthetized with sodium pentobarbital but in addition given heparin and a fat-albumin infusion to elevate FFA. Stimulating the nerves to a group of skeletal muscles in the hindlimb (1.5/s) increased muscle blood flow 2.4-fold in both groups. In the first group stimulation did not alter the arteriovenous difference of lactate across the muscles. The difference was close to zero before and during stimulation. However in the second group, in which FFA were elevated, stimulation produced a large increase in muscle lactate production. In both groups there were no differences in the L/P ratio of muscle venous blood during stimulation. These results indicate that an increase in lactate production following muscle stimulation is not necessarily related to a state of tissue hypoxia.

The effect of five per cent carbon dioxide on the response of muscle blood flow to isoproterenol in man.

Heart rate, muscle blood flow, and blood pressure were measured in 10 subjects. The administration of 5 per cent CO2 caused a fall in blood flow and an increase in mean arterial pressure without significant change in heart rate. An infusion of isoproterenol at a dose of 2 ug per minute caused an increase in flow, heart rate, and pulse pressure but no change in mean arterial blood pressure. The administration of 5 per cent CO2 during the isoproterenol infusion abolished the increase in muscle blood flow, produced an increase in mean arterial blood pressure, and caused an attenuation of the chronotropic effect of isoproterenol. These results suggest that certain cardiovascular effects of isoproterenol are altered during respiratory acidosis.

Increase in skeletal muscle performance during emotional stress in man.

An emotional stress arising as a result of intense mental arithmetic causes (in most subjects) an increase in blood flow through resting forearm muscle by an average of 85%. Combination of voluntary sustained handgrip contraction with mental arithmetic has shown that the duration of contraction increases by an average of 46%. This effect appears only in subjects who display an increase in blood flow as a result of mental arithmetic. A rise in muscle performance is also observed during mental arithmetic when contraction of forearm muscle is caused by direct stimulation of the motor nerve in the upper arm. Intra-arterial injection of atropine sharply reduces both the increase in blood flow through the resting muscle and the increase in muscle performance associated with mental arithmetic. Control performance (without mental arithmetic) is not altered by administration of atropine. Analysis of blood flow during muscle contraction leads to the conclusion that an increase in muscle performance during emotional stress is not dependent on an increase in muscle blood flow. The data suggest that during emotional stress the sympathetic nervous system causes metabolic changes in skeletal muscles that lead to an increase in muscle performance when oxygen deficiency exists.

Bulbar and suprabulbar control of the cardiovascular autonomic effects during arterial hypoxia in the rabbit.

The autonomic effects on heart rate, portal, renal, cutaneous and muscle blood flows were studied during approximately constant severe arterial hypoxia in unanesthetized sham-operated, thalamic and pontine rabbits, 3 hours after operations conducted under halothane anesthesia. Neural and adrenal effects were estimated by comparing the responses of different groups of animals: (a) with all neural effectors intact, (b) after adrenalectomy, (c) after selective and (d) after complete pharmacological block of neural effector mechanisms. In pontine animals hypoxia greatly increased cardiac sympathetic activity and seemed to evoke a greater release of adrenal catecholamine (epinephrine) than in other preparations, but caused significant neural peripheral sympathetic constrictor effects in only the portal bed. In thalamic animals, hypoxia caused reflex bradycardia, striking neural constrictor effects in the portal, renal and muscle beds, and cutaneous dilatation. There was little evidence of an increase in epinephrine secretion. It is suggested that there is an inhibitory pathway between diencephalon and bulb that limits the release of epinephrine. Sham-operated animals exposed to hypoxia secreted epinephrine which played an important role in the total reflex response; this group had similar cardioinhibitory and cutaneous effects to thalamic animals, but a more rapid onset of portal and renal constriction and a marked increase in muscle blood flow. The sympathetic responses of the different preparations resulted in different rates of metabolic H + ion production.

The mechanism of the increased maximum work performance of small muscle groups resulting from "diverting work" with other muscle groups.

AbstractThe mechanism of increased work performance resulting from “diverting works” was examined. Muscle blood flow was measured in exercised and rested muscles by means of venous occlusion plethysmography and 133Xe clearance. Measurements of muscle blood flow, blood pressure and work performance following “diverting work” and other stimuli were compared with values obtained during control rest periods. Stimuli which caused a substantial rise in arterial blood pressure (“diverting work”, change in heart level, pain) caused increases in blood flow and work performance in exercised muscles. Non‐pressor or mild pressor stimuli (non‐strenuous “diverting work”, CO2 inhalation, apnea, cold) resulted in unchanged blood flow and work values in the exercised muscles. It is concluded that pressor stimuli produce increased muscle blood flow in maximally ischemic muscles due to release of muscle arteries from neurogenic and myogenic control. The increased muscle blood flow during periods employing pressor stimuli results in improved muscle restitution and hence increased work performances.

Application of Pavlovian concepts to anxiety and forearm blood flow.

Forearm blood flow is presented as an objective index of anxiety. The mechanism by which increase in muscle blood flow occurs as part of a co-ordinated response to “fight or flight” in animals and in man is discussed. An increased forearm blood flow may indicate a considerable degree of internal agitation, although a patient may appear outwardly calm, and this is thought to be evidence of schizokinesis. Patients with anxiety often experience panic attacks with considerable physiological arousal and this may lead to one-trial conditioning. Autokinesis may result in the development of further symptoms, and the Effect of Person on the cardiovascular system in animals and man is considered. Conditionability of anxious patients was investigated and the acquisition and extinction rates of conditional eyelid responses were found to be similar in a group of patients with anxiety, a variety of psychoneurotic disorders, and normal controls. The use of forearm blood flow to monitor reduction in anxiety brought about by medication, desensitization and psychotherapy has been found to be a valuable addition to the objective methods of assessment in psychiatry.

Oxygen uptake in skeletal muscle of the anesthetized dog during sympathetic vasodilatation.

AbstractSympathetic, cholinergic kasodilatation in skeletal muscle was induced as orienting and conditional reflex responses in conscious dogs. A sound stimulus elicited an orienting reflex accompanied by an atropine‐sensitive vasodilatation in the skeletal muscles of the hind limb. Further, a tachycardia and a slight blood pressure rise were noticed. The orienting reflex response disappeared gradually on repetition of the sound stimulus. The same cardiovascular events were obtained as conditional reflexes to both electrical cutaneous stimulation and exercise on a treadmill. The conditional responses were not diminished if the conditional reflexes were reinforced by training. Graded conditional responses were obtained when the intensities of the unconditional stimuli were varied. The increase in blood flow to the hind limb following treadmill exercise was not influenced by atropine. Our findings indicate that the sympathetic vasodilator system is activated prior to situations when an increased muscle blood flow is suddenly required. The results also suggest that activation of the dilator nerves takes place not only in emotionally charged situations, such as the defence reaction, but also in anticipation of exercise when the emotional involvement is less prominent.

Cardiovascular changes during naturally elicited fighting behavior in the cat.

Cardiovascular changes during naturally elicited fighting behavior in the cat.

Muscle and skin clearance of antipyrine from exercising ischemic legs before and after vasodilating trials.

Abstract In a series of patients with intermittent claudication, antipyrine labelled with iodine isotopes was deposited in the calf muscle and skin of the lower leg. The disappearance rates of the tracers were utilized to evaluate changes in the regional blood flow in connection with exercise on a foot ergometer. The clearance curves suggested that, besides an increase of muscle blood flow, there was a gradual diversion of blood flow from the skin during exercise, with a transitory period without any removal of tracer from the skin depot towards the end of exercise but particularly immediately afterwards. The duration of this latter period was correlated to the degree of arterial obliterative disease in the leg and was considered useful in the diagnosis of incipient peripheral ischemia.The ability of conventional vasodilating drugs to influence the behaviour of these clearance curves during exercise was tested in acute clinical experiments. It was found that, irrespective of the pharmacological mode of action, parenteral administration of the drugs used was accompanied by a significant decrease in clearance rate from the active muscles as compared with that registered during exercise of identical intensity before the therapeutic trial. Simultaneously there was a tendency to a delayed elimination of the skin tracer. The deleterious effect of the drugs on the clearance rates and thus presumably on the peripheral blood flow in the presence of arterial insufficiency seemed to be related to their depressive influence on the mean arterial blood pressure, brought about by an extensive dilation of healthy vascular beds.

Peripheral circulatory and metabolic consequences of thyrotoxicosis. I. Blood flow and oxygen consumption of resting and working skeletal muscle in experimental thyrotoxicosis in the dog.

Frey, H. M. M. Peripheral Circulatory and Metabolic Consequences of Thyrotoxicosis I: Blood flow and oxygen consumption of resting and working skeletal muscle in experimental thyrotoxicosis in the dog. Scand. J. din. Lab. Invest. 19 4-14, 1967. Blood flow and oxygen consumption of the gracilis muscle have been measured in the anesthetized, thyrotoxic dog.The thyrotoxicosis was accompanied by an increase in the oxygen consumption of resting muscle. The relative increase was greater than for the body as a whole. The elevated oxygen consumption of thyrotoxic muscle was accompanied by a proportional increase in muscle blood flow, arteriovenous oxygen difference remaining unchanged. The increase in blood flow through the resting gracilis muscle was proportional to the increase in cardiac output.Oxygen consumption during isometric contractions in response to electrical stimulation of the motor nerve was studied at various stimulation frequencies. An increase in the number of contractions per second caused a gre...

Effect of a new hypotensive drug, ST155, on the systemic circulation

Dogs on heart-lung bypass and perfused gracilis muscle preparations were used to investigate the effect of the recently introduced hypotensive drug, ST155, on the systemic circulation. Five micrograms per kilogram of ST155 caused a transient rise followed by a sustained fall in the perfusion pressure of dogs on heart-lung bypass. Changes in the regional distribution of blood were associated with these changes in perfusion pressure, the hypotensive response being associated with a marked increase in muscle blood flow. Phenoxybenzamine failed to abolish the initial pressor action of ST155; propranolol and Ansolysen abolished its hypotensive action. ST155 failed to affect the perfusion pressure in isolated gracilis muscle preparations perfused under conditions of constant flow.

Cardiovascular Effects of Acute and Chronic Stimulations of the Hypothalamic Defence Area in the Rat

AbstractIn experiments on rats long‐term intermittent stimulations of the hypothalamic defence area have been performed after that the characteristic responses to such stimulations had been explored in acute experiments. Weak topical stimulations of the defence area in rats induced an alerting response which was regularly accompanied by blood pressure and heart rate increases, increased muscle blood flow and decreased renal and gastrointestinal blood flows. When such weak intermittent stimulations of the hypothalamic defence area were continued for 12 hours daily during about four months the ‘resting’ blood pressure of a stimulated group of rats gradually rose, to become significantly different from that of a control group, which had been identically treated in all respects with exception of the intermittent hypothalamic stimulations. On the basis of these results it is discussed whether episodes of mental stress, which are often repeated during prolonged periods of time and which normally seem to excite the hypothalamic defence area, may act as an efficient “trigger” mechanism for gradually inducing a stage of chronic hypertension.

The control of the circulation in skeletal muscle during arterial hypoxia in the rabbit.

1. The effects of arterial hypoxia on muscle blood flow were examined in normal unanaesthetized rabbits in relation to simultaneously determined changes in cardiac output, arterial pressure and heart rate. Muscle blood flow was estimated from the difference between total limb flow (local thermodilution) and the estimated skin flow (using a calibrated heat conductivity method). The role of the arterial chemoreceptors and baro-receptors in the control of muscle blood flow was examined and the nature of the sympathetic efferent discharge analysed.2. In mild hypoxia (P(O2) > 35 mm Hg) in the rabbit, muscle blood flow did not change, although cardiac output increased. During moderate hypoxia (P(O2) 30-35 mm Hg) there was initial vasoconstriction in muscle, followed by a return to control values paralleling the changes in cardiac output. In severe arterial hypoxia (P(O2) < 30 mm Hg) the initial vasoconstriction was less marked, and during the ;steady state' there was a large vasodilatation and increase in muscle blood flow, at a time when the cardiac output was not elevated.3. The early vasoconstriction in arterial hypoxia is mediated mainly through sympathetic vasoconstrictor nerves as a result of strong arterial chemoreceptor stimulation.4. Increased secretion of adrenaline is an important factor in restoring muscle blood flow to control values during moderate arterial hypoxia, and in elevating the muscle blood flow above these values in severe hypoxia. The peripheral dilator (beta-) effects of adrenaline oppose the peripheral constrictor (alpha-) effects resulting from increased activation of sympathetic constrictor nerves during arterial hypoxia.

Effects of Epinephrine on Cardiovascular and Metabolic Responses to Leg Exercise in Man

In studies on six experienced subjects lying supine, cardiac output and oxygen content of femoral venous blood were measured with the subject at rest, during the increase in muscle blood flow caused by intravenous infusion of epinephrine, during mild leg exercise, and during identical exercise combined with an infusion. The oxygen content of the blood from the exercising limb was much higher (average, 50%) during an infusion than when no infusion was given (average, 32%). The mean increase in cardiac output during the combined maneuver (8.2 liters/min) almost equaled the sum of the increases during the separate infusion (3.7 liters) and during exercise (4.7 liters). All individual studies showed approximately this same result. Thus, the additional blood supplied to the leg muscles by the infusion did not appear to be used for metabolic purposes during exercise. cardiac output; muscle blood flow Submitted on March 22, 1963