The action of adrenaline on muscle blood flow and blood lactate in man

Muscle blood flow response to mental stress and adrenaline infusion in man: microdialysis ethanol technique compared to (133)Xe clearance and venous occlusion plethysmography

BACKGROUND AND AIM

Adrenaline, administered locally by microdialysis in skeletal muscle, causes vasoconstriction around the microdialysis catheter. This is contrary to the vasodilation that normally occurs when adrenaline is infused intravenously or intra-arterially. The hypothesis was tested that vasoconstriction, measured by microdialysis, would not occur with two interventions causing increased plasma levels of adrenaline, mental stress and intravenous adrenaline infusion (0.1 nmol kg(-1) min(-1)).

METHODS

Twenty-four men (27 +/- 1.6 years) underwent these interventions. Blood flow was determined by the microdialysis ethanol technique and (133)Xe clearance (gastrocnemius muscle, medial head) and by venous occlusion plethysmography (calf).

RESULTS

The ethanol outflow/inflow ratio, which is inversely related to blood flow, decreased to 92.0 +/- 3.4% of basal, P = 0.014 (mean +/- SEM, n = 16) during the mental stress test, but increased to 108.3 +/- 2.2% of basal, P = 0.001 (n = 16) during the adrenaline infusion. The latter increase was abolished when adrenaline was infused during alpha-receptor blockade by phentolamine. On the contrary, by (133)Xe clearance and venous occlusion plethysmography, blood flow increased during both interventions; 2.0-1.7-fold (mental stress) and 1.3-1.4-fold (adrenaline infusion), respectively, P<0.05.

CONCLUSION

Adrenaline causes vasoconstriction in skeletal muscle when blood flow is measured with the microdialysis ethanol technique, irrespective of the mode of administration. The discrepant blood flow result obtained with the microdialysis ethanol technique might, at least partly, be explained by differential diffusion properties of ethanol and (133)Xe. An additional or alternative explanation might be that an inserted microdialysis catheter shifts the balance of vasoconstrictor and vasodilator effects of adrenaline in skeletal muscle.

Inhibition of plasma kininase activity at slightly acid ph

Kinins, like bradykinin, are rapidly inactivated in blood and interstitial fluid by an enzyme called kininase. The action of this enzyme was found to be inhibited at slightly acid pH although the formation of kinins proceeded normally. Thus a slightly acid pH which is known to occur in inflamed and damaged tissue is a suitable environment to allow accumulation of kinins which are thought to be the mediators of the inflammatory response.

Glucose and free fatty acid turnover in thyrotoxicosis and hypothyroidism, before and after treatment

Glucose and free fatty acid (FFA) turnover (RT) were measured by isotopic methods in groups of patients with thyrotoxicosis and hypothyroidism and compared with normal subjects. Patients with thyrotoxicosis were then studied after treatment with oral propranolol and again after treatment with carbimazole. Patients with hypothyroidism were studied again after treatment with thyroxine. Glucose RT was increased by about a third in thyrotoxicosis (12.7 mumol. min.-1 kg-1 +/- 1.0 SEM compared to 9.5 +/- 0.5 in normal subjects) while FFA RT was doubled (12.5 mumol. min.-1 kg-1 +/- 1.2 compared to 6.3 +/- 0.9 in normals). Propranolol was without effect, but carbimazole normalized these variables. In hypothyroidism both glucose and FFA RT were normal (9.1 +/- 0.7 and 6.7 +/- 0.9 respectively). Mean glucose and FFA RT both rose following thyroxine treatment, but not significantly; the post-treatment values remaining within the normal range (10.3 +/- 0.7 and 7.0 +/- 1.3 respectively). Oxidation of FFA, as estimated by 14CO2 excretion, was increased in thyrotoxicosis (42.8% +/- 2.9 SEM compared to 34.8 +/- 2.3 in normal subjects) and fell with carbimazole treatment (34.7 +/- 4.1). In hypothyroid subjects FFA oxidation increased following thyroxine treatment (from 34.4 +/- 4.1). In hypothyroid subjects FFA oxidation increased following thyroxine treatment (from 34.4 +/- 3.3 to 46.2 +/- 3.6).

Relationship between the metabolic and vasodilator effects of epinephrine in human forearm muscle

The effect of intra-arterial and intravenous epinephrine on skeletal muscle blood flow and metabolism were studied in the human forearm following complete suppression of the circulation to forearm skin by epinephrine inotophoresis. Epinephrine by either route of administration increased blood flow, O 2 consumption and CO 2 production, and decreased arteriovenous differences of O 2 and CO 2 across the forearm. The increments in blood flow did not correlate with the increments in O 2 consumption or CO 2 production. In the intact forearm intravenous epinephrine increased deep forearm venous Po 2 but not venous PCo 2 . Hypocapnia, induced by voluntary hyperventilation, did not alter the response of forearm blood flow to intravenous epinephrine. These results show that the vasodilator response of skeletal muscle vessels to epinephrine is not dependent on decrease in Po 2 or increase in PCO 2 in the environment of the high resistance vessels. They also suggest that the calorigenic effect of the hormone is not a dominant factor in its vasodilator effect in skeletal muscle.

A CASE OF MCARDLE'S SYNDROME WITH A POSITIVE FAMILY HISTORY

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