1. Asthmatic patients bronchodilate in response to infused atrial natriuretic factor. We wished to determine whether the airways of normal subjects responded in a similar way. 2. Changes in airway resistance, as determined by specific airway conductance, were measured in eight normal subjects in response to intravenous infusion of atrial natriuretic factor at doses of 0.5, 2 and 10 pmol rnin −1 kg −1 . 3. No significant effect was observed on specific airway conductance at any rate of infusion despite maximum mean (sem) plasma levels of 597 (62) pg of atrial natriuretic factor/ml in peripheral venous blood. 4. A second study was performed using six of the eight original subjects and employing a pharmacological dose of 50 pmol of atrial natriuretic factor min −1 kg −1 . This produced mean plasma levels of 2056 pg/ml and a mean increase of 31% in specific airway conductance. 5. It is concluded that pharmacological, but not pathophysiological, elevations of plasma atrial natriuretic factor may significantly alter bronchomotor tone in normal subjects.
1. Airway, cardiovascular and metabolic responses were measured in six asthmatic patients with stable asthma during separate adrenaline, noradrenaline and control infusions. Four incremental infusion rates (4, 10, 25 and 62.5 ng min −1 kg −1 ) produced circulating catecholamine concentrations within the physiological range. 2. Specific airways conductance and maximal expiratory flow rates measured from complete and partial flow-volume curves increased significantly ( P < 0.05) during adrenaline infusion, in a dose-response manner. 3. No changes in specific airways conductance or maximal expiratory flow rates were seen during the noradrenaline or control infusion. 4. The highest adrenaline infusion rate caused a rise in systolic blood pressure ( P < 0.05) and plasma glucose ( P < 0.05) and a fall in plasma potassium ( P < 0.05). 5. Noradrenaline infusion caused a slight increase in diastolic blood pressure ( P < 0.05) but no metabolic changes. No cardiovascular or metabolic changes occurred during the control infusion. 6. Infused adrenaline, producing circulating concentrations within the physiological range, caused dose-related bronchodilatation in asthmatic patients. Circulating noradrenaline does not appear to have a role in the control of basal airway tone in asthmatic patients.
1. The bronchial response to an anaesthetic aerosol of 4% bupivacaine hydrochloride has been investigated in normal and asthmatic subjects. 2. No significant changes in specific conductance were seen in normal subjects. In asthmatic subjects a significant fall in specific conductance occurred which was significantly reduced by prior treatment with ipratropium bromide. 3. Aerosols of bupivacaine, sodium cromoglycate and saline were tested on the cough reflex elicited by citric acid aerosol in normal and asthmatic subjects. Bupivacaine, but not the other agents, abolished the cough reflex in both groups of subjects. 4. Ipratropium bromide and bupivacaine were tested on methacholine-induced bronchoconstriction in normal and asthmatic subjects. Ipratropium bromide significantly prevented the fall in specific conductance in both groups of subjects whereas bupivacaine (normal subjects only tested) had no protective effect. 5. Ipratropium bromide, bupivacaine and sodium cromoglycate were tested on histamine-induced bronchoconstriction in normal subjects. Half the normal subjects had an upper respiratory tract infection. Ipratropium bromide significantly reduced the fall in specific conductance at 1 min after histamine but not at 5 or 10 min. Bupivacaine and sodium cromoglycate had no protective effect on histamine-induced bronchoconstriction at 1, 5 and 10 min. 6. Ipratropium bromide and bupivacaine were tested on prostaglandin F 2 α-induced bronchoconstriction in normal subjects. Neither drug prevented the change in specific conductance after prostaglandin F 2 α. 7. The possible significance of these results is discussed in relation to vagal mechanisms in the control of airways calibre in normal and asthmatic subjects.