Effect of cocaine and related drugs on the uptake of noradrenaline by heart and spleen

Noradrenaline uptake by heart and spleen after intravenous infusion of noradrenaline was measured in the pithed rat. Cocaine, given before the infusion, inhibited the noradrenaline uptake in relation (a) to the dose administered and (b) to the amount of noradrenaline infused. There was an association between increase in the pressor response to a test dose of noradrenaline and inhibition of the uptake by the heart. Drugs related chemically to cocaine, such as alpha-cocaine, amethocaine, and atropine, did not alter the noradrenaline uptake or potentiate the blood pressure response to noradrenaline. The noradrenaline uptake by the heart was unchanged after dibenamine, but blocked by the dichloro-analogue of isoprenaline. It was concluded that cocaine specifically prevented the uptake of noradrenaline by tissues, thus increasing the amount of noradrenaline available for combination with adrenergic receptors. The dichloro-analogue of isoprenaline appeared to block both uptake by the heart and the combination with receptors.

Effect of reserpine on the acetylcholine content of the heart, the ileum and the hypothalamus of the dog

The effect of intravenous administration of reserpine in 10 dogs was studied on the acetylcholine content of the sino-atrial node, the right auricle and the right ventricle of the heart, the ileum and the hypothalamus of dog. The general sedation, the bradycardia, and the purgative effects of reserpine were also noted. Tissues were removed for estimation of acetylcholine when bradycardia was maximal. Reserpine increased the acetylcholine content of all the tissues studied. The increase in the peripheral tissues was greater than in the hypothalamus. The bradycardia and the purgative effects of reserpine may be related to the increase of the acetylcholine content of the sino-atrial node and the ileum.

Ouabain-induced ventricular tachycardia and its effect on the performance and metabolism of the dog heart

At constant pressure work there was an increase in the oxygen consumption of the dog heartlung preparation after tachycardia due to auricular stimulation and a far greater increase in consumption after ouabain-induced ventricular tachycardia, as compared with control hearts beating at their own sinus rhythm. In neither condition was the increase in coronary flow greater than the spontaneous increase in the controls. It is suggested that an increase in oxygen demand, under certain circumstances, may be met primarily by an increased desaturation of coronary blood. "Therapeutic" doses of ouabain did not improve the mechanical efficiency of the preparation. "Toxic" doses of ouabain which gave rise to ventricular tachycardia did not decrease the phosphocreatine or labile nucleotide phosphorus content of the heart provided there was no hypoxia of the heart muscle.

The rate of oxygen uptake of quiescent cardiac muscle

The rate of oxygen uptake of quiescent papillary muscle of the cat heart has been determined in a flow respirometer with the use of the oxygen electrode. The apparent rate of oxygen uptake as a function of the diameter of the muscle was also determined. It was found that papillary muscles from cat hearts use oxygen at a rate of 2.84 (microliters/mg. wet weight)/hour at a temperature of 35°C. Such muscles can be adequately supplied by diffusion when their surface is uniformly exposed to an atmosphere containing 95 per cent oxygen only if their diameter is 0.64 mm. or less. Papillary muscles from kitten hearts use oxygen at a rate of 4.05 (microliters/mg. wet weight)/hour at a temperature of 35°C. Such muscles can be adequately supplied by diffusion when their surface is uniformly exposed to an atmosphere containing 95 per cent oxygen only if their diameter is 0.53 mm. or less. If the muscles are small enough to be adequately supplied with oxygen by diffusion, the rate of oxygen uptake does not increase when the muscle is stretched.

Myocardial removal of free fatty acids under normal pathological conditions

Myocardial arteriovenous difference in free fatty acids (FFA) and coronary flow was determined in dogs under morphine-chloralose anesthesia. Fifteen minutes after the administration of insulin the A-V difference decreased. FFA uptake did not change significantly. Alloxan diabetes decreased the utilization per cent of FFA. Norepinephrine elevated myocardial uptake and arterial FFA. Hypoxia did not change FFA uptake. Hypothyroidism lowered myocardial uptake. Left ventricular O2 consumption increased after administration of atropine in both normal and hypothyroid animals, whereas hypothyroidism was associated with a decreased value. A significant correlation was found in normal dogs between arterial FFA concentration and myocardial uptake. A different relationship suggested itself in hypothyroid animals. A correlation was also shown between the per cent of myocardial O2 consumption calculated for complete oxidation of FFA and the myocardial R.Q.

Myocardial blood flow and oxygen consumption during postprandial lipemia and heparin-induced lipolysis

The role of the physical state of plasma as a determinant of oxygen availability to the myocardium has been investigated during the course of alimentary lipemia. After the development of substantial plasma lactescence, the coronary blood flow (nitrous oxide method) and myocardial oxygen consumption were assessed in 7 normal human subjects and repeated after heparin-induced lipolysis. The lipemic state was further contrasted with a control fasting group, comparable in age and sex.

The mean coronary blood flow for 15 fasting controls was 83 ml. per 100 Gm. of left ventricle per minute with a myocardial oxygen extraction of 11.04 volumes per cent, and a myocardial oxygen consumption of 9.0 ml. per 100 Gm. of left ventricle per minute. By contrast, the mean coronary blood flow during maximal lipemia in the 7 subjects fed cream was 20 per cent below normal, with a value of 67 ml. per 100 Gm. per minute ( p =< 0.01). As the extraction of oxygen was not significantly affected, the calculated myocardial oxygen consumption was proportionately reduced to 7.02 ml. per 100 Gm. per minute ( p =< 0.01). A failure of the anticipated oxygen extraction increment in the face of coronary blood flow reduction suggests an impediment of blood-tissue oxygen transport during lipemia.

After the administration of 60 mg. of heparin to the 7 lipemic subjects, a 65 per cent decline in plasma lactescence was observed by 45 minutes, when the coronary blood flow and myocardial oxygen consumption were elevated to 87 ml. per 100 Gm. per minute ( p =< 0.05) respectively. Thus, the reduced coronary flow and myocardial oxygen consumption were restored in each instance to normal levels during the process of plasma clearing. There were no associated systemic hemodynamic changes to account for such increments. These heparin effects appear dependent on the lipemia-clearing property, for no alteration in coronary dynamics was found in 6 additional patients in whom this activity was not manifest after the same heparin dosage.

The residual lactescence after post-heparin lipolysis was associated with no significant deviation of coronary dynamics from the normal. That a concentration-dependent phenomenon is operative, was confirmed in a separate group of patients in whom low lactescence values developed in the course of alimentary lipemia without affecting myocardial oxygen consumption.

The relevance of the lipemic state, per se, to the pathophysiology of myocardial ischemia appears to depend upon the establishment of an oxygen gradient within the myocardium, presumably through altered pressure-flow relationships produced by lipemic blood within a pathologic vessel.

Potassium loss from the heart during the immediate posthypercapnic period

Experiments have been carried out on mongrel dogs in which plasma potassium concentrations in blood samples simultaneously drawn from the aorta and coronary sinus have been determined before, during and following 4 hours of high CO2 breathing. No significant difference between potassium concentration in aorta and coronary sinus blood was evident before or during breathing of high CO2 mixtures. Five minutes after returning to air breathing however, coronary sinus plasma potassium concentration was significantly elevated above that of the aorta. This loss of potassium from the heart is accompanied by severe cardiac irregularities, premature systoles, ventricular tachycardia and, sometimes, ventricular fibrillation. Coronary blood oxygen concentration differences decrease significantly during hypercapnia, and estimates by the N2O technique indicate that this decrease is the result of an increase in coronary flow.

Uptake of labelled noradrenaline by isolated atria

The uptake of labelled noradrenaline by isolated rabbit atria has been studied, and the rate of outflow of radioactivity after a period of loading has been recorded. There is first a rapid outflow presumably from extracellular space, followed by a slow outflow presumably from intracellular space. Cocaine greatly diminished the intracellular uptake. Tyramine caused an increased outflow of radioactivity from intracellular sites which was not due to the increase in atrial rate, since noradrenaline which increased the rate more than tyramine had less effect on the outflow.