Shigeaki Ikeda

Microcirculation in the Ventricle of the Dog and Turtle

Phasic red cell velocity and diameters of coronary arterioles, capillaries, and venules were measured in the beating turtle and dog heart using high-speed cinematography with transillumination of the left ventricle. In the turtle, arteriolar red cell velocity was diminished during systole, but during diastole arteriolar inflow increased, especially during the rapid and the slow filling period. Capillary and venule red cell velocity was increased during systole, particularly at the time of ejection; however, during diastole red cell velocity declined and the lowest values occurred during isovolumic relaxation. In dog arterioles, capillaries, and venules, the pattern of red cell velocity was similar. Thus, in the turtle and dog, the peak arteriolar red cell velocity occurred in unison with left coronary artery inflow, and the capillary and venule flow pattern followed that of the coronary sinus. The diameters of arterioles, capillaries, and venules in the turtle ventricle all declined about 34% during systole; similar results were obtained in the dog. Capillary arrangement appeared to be predominantly parallel and cocurrent; however, capillary loops with countercurrent flow were occasionally observed. The data on microvascular phasic red cell velocity are consistent with the macroobservations of reduced coronary artery inflow and enhanced coronary sinus outflow during ventricular contraction. The results demonstrate that the shift in the flow pattern occurs at the transition from arterioles to capillaries.

Biochemical and contractile properties of heart muscle after prolonged alcohol administration

Abstract This report deals with the correlation of changes in cardiac metabolism and myocardial contractility of dogs maintained on alcohol for 29 months. Glycerinated heart muscle fibers were used to investigate myocardial contractility in vitro, using an apparatus to record isometric and isotonic contractions. Measurements included maximal tension developed (Po), maximal rate of tension developed ( d p d t max ), and time to peak tension (to). Force-velocity relationship (Vmax) was also determined. Biochemical studies revealed significant depression of mitochondrial respiration in heart muscle of dogs exposed to alcohol. Calcium uptake and binding to sarcoplasmic reticulum and its endogenous calcium content were diminished. The activity of intramitochondrial isocitrate dehydrogenase was also decreased. Hemodynamic changes in vivo revealed no significant difference between control animals and dogs maintained on alcohol. In vitro studies on glycerinated heart muscle of dogs exposed to alcohol showed no change in d p d t max , to or Po. Values for Vmax were significantly reduced. The results suggest that while the contractile apparatus in heart muscle exposed to alcohol can generate maximal tension, it is deficient in its property to perform external work. Contractile changes in heart muscle of animals exposed to alcohol can exist in vitro, without apparent hemodynamic alterations in vivo. It is not certain whether these changes in vitro are the result of direct action of alcohol on contractile proteins, or develop as a consequence of biochemical changes induced by alcohol.

The effect of carbon monoxide on lipid metabolism of human coronary arteries

Human coronary arteries were perfused under sterile conditions in vitro with blood containing high or low concentrations of carbon monoxide. Lipid synthesis in the arterial wall was investigated by incorporating [14C]acetate; synthesis of the following lipids was measured: cholesterol, cholesterol ester, di- and triglycerides and phospholipids. Cholesterol uptake by the arterial wall was studied by using [3H]cholesterol as a tracer. No influence of CO on lipid synthesis in the arterial wall could be demonstrated. In contrast, arteries which were exposed to CO showed a higher uptake of cholesterol as compared to their corresponding control. The concentration of CO in the perfusate did not alter the degree of cholesterol uptake. These results are in general agreement with those of others, who found that CO significantly increases the permeability of endothelial membranes.

Myocardial Blood Flow

It is generally agreed that coronary inflow is mainly diastolic and coronary sinus outflow mainly systolic (Gregg, 1962). To locate this phase shift, phasic red cell velocity and diameters of coronary arterioles, capillaries, and venules were measured in the beating turtle and dog heart using high-speed cinematography (400 frames/s) with transillumination of the left ventricle. A 20-gauge needle, containing a small quartz rod and a mirror angled at 45°, was inserted underneath the superficial layer of the myocardium to transmit heat-filtered light from a pulsating xenon arc through the ventricular muscle toward the objective of an infinitycorrected microscope. In recent experiments, a floating, counterbalanced focus keeper was used to maintain the focal distance between the moving heart and the stationary objective of the microscope. Red cell velocity was determined by frame-to-frame analysis of red cell progression using a reference scale (Tillich et al., 1971; Bing et al., 1972)

Lipid metabolism in perfused human and dog coronary arteries

The paper represents a summary of our studies in which in vitro perfusion of human and animal coronary vessels was carried out. Formation and uptake of lipids in perfused human coronary arteries were studied under a vairety of experimental conditions, including exposure to carbon monoxide. The effect of collagenase on lipid synthesis and transport in carotid arteries of dogs was also studied. Human plasma with hydrogen-3-labeled cholesterol and carbon-14-acetate was used to perfuse human blood vessels. Autologous plasma was employed. Inhibition of cholesterol uptake was accomplished by the addition of 7-ketocholesterol (concentrations of 0.005 to 1 mum/ml) to the perfusate. Both atherosclerotic and normal human coronary arteries incorporated 14C-acetate into lipids but failed to synthesize either cholesterol of cholesterol esters. Similar results were obtained in human saphenous veins perfused at arterial pressure. Cholesterol uptake from the perfusion fluid was demonstrated in atherosclerotic and normal human coronary arteries as well as in human saphenous veins. Carbon monoxide increased permeability of the arterial wall to cholesterol uptake. In dog arteries exposed to collagenase marked increases in cholesterol uptake were found, but total lipid synthesis was reduced; the relative synthesis individual lipids remained unchanged. The addition of 7-ketocholesterol to the perfusate reduced cholesterol uptake by the vessel by 90 percent. Inhibition of cholesterol uptake was present in all species and was not due to oxidation of cholesterol to 7-detocholesterol in the perfusate. The results illustrate that human coronary arteries as well as human saphenous veins synthesize lipids but not cholesterol. Cholesterol flux into the artery is augmented by carbon monoxide and collagenase. The data also show that active inhibition of cholesterol uptake in the arterial wall can be accomplished by competitive inhibition with 7-ketocholesterol.

METABOLIC EFFECTS OF ALCOHOL ON THE HEART

The relationship between heart disease and alcoholism was apparently first described by Walshe in 1873.’ The expression “alcoholic cardiomyopathy” was coined by Mackenzie in 1902.2 Prior t o this, in 1884, Bollinger described the Munich beer heart (cardiac hypertrophy existing in beer The statistics presented by Bollinger are interesting: In 1884, he found in Munich a beer consumption of 432 liters per head of population; this included newborns. In 1929, Wenckebach first described beri-beri heart disease? and since that time many of the effects of alcohol on the heart have been thought t o be the result of nutritional deficiencies. This is not the case, as demonstrated recently by Robin and Gold~chlager ,~ who reported a patient with alcoholic noncirrhotic beri-beri heart disease, developing low cardiac output failure shortly after successful treatment with thiamine. In 1966, Wendt and associates published a paper on the acute effect of alcohol on the human myocardium,6 followed by another study on the effect of chronic alcoholism on cardiac metabolism in man.’ Wendt was able t o observe the release of intramyocardial enzymes into coronary vein blood and proposed that alcohol might alter membrane permeability and impair the activity of metabolic pathways.’ This assumption has been supported by autopsy determination of the activities of several enzymes in the left ventricle of patients who died of alcoholic cardiomyopathy.8 Analysis of the specimens demonstrated a marked reduction in cellular activity of certain oxidative enzymes, such as NAD-dependent isocitrate dehydrogenase (NADICDH), and a significant increase in the activity of some glycolytic enzymes, particularly glyceraldehydephosphate dehydrogenase, the enzyme responsible for the glycolytic substrate phosphorylation. An accumulation of triglycerides in the heart muscle of animals exposed t o alcohol was demonstrated by Regan et al. in 1966.9 This observation has been confirmed by Marciniak e t al.l0 Alcohol may affect both cardiac contractility and metabolism. Despite marked changes in cardiac metabolism, ethanol results in clear-cut changes in myocardial contractility only after many years of exposure. Before entering into a discussion of effects of ethanol on heart muscle, it is necessary to discuss briefly some of the possible mechanisms that can result in disturbance of myocardial contractility. This subject has developed into a very active field of investigation because of its possible clinical implications. In discussing this field, the possible actions of ethanol on subcellular organelles, such as the sarcoplasmic reticulum, the mitochondria, and the contractile proteins, must be considered.

In Vivo Inhibition of Cholesterol Uptake in Rabbit Aortas by 7-Ketocholesterol

Summary The iv injection of 7-ketocholesterol into rabbits, made soluble by combining with bile salts, inhibited cholesterol uptake by the aorta. However, the inhibition was not as marked or as uniform as previously demonstrated in in vitro experiments. This difference may have been the result of lower plasma concentrations of 7-ketocholesterol in the injected animals. Gastric feeding of 7-ketocholesterol failed to inhibit aortic cholesterol uptake, probably because of inadequate plasma concentrations of the inhibitory steroid. The results suggest that the mechanism of 7-ketocholesterol on aortic cholesterol uptake is through competitive inhibition. The authors wish to express their thanks to Mrs. Arpine Grenier and Mrs. Elana Colby for their technical assistance, and to Miss Barbara Biedebach and Mrs. Cindy Curry for their help in the preparation of this manuscript. We also appreciate the advice of Dr. George Popjak.

The Effect of Nicotine on the Coronary Microcirculation in the Cat Heart

T HE effect of nicotine on coronary blood flow and contractile force of the heart has been the subject of a series of investigations. Several studies have described an increase in total coronary flow following smoking in human subjects without coronary artery disease’ and after intravenous injection of nicotine.’-’ Other investigators have also demonstrated an increase iii heart rate, cardiac output, and systemic blood pressure.3-’ It ahso has been demonstrated that nicotine increases both coronary capillary blood flow and terminal coronary vascular capacity5#{176} together with coronary red cell velocity.’0 These effects of nicotine could have beeii caused by a systemic effect of the drug (primarily an elevation in systemic blood pressure) or by release of catecholamines from the heart directly. \Vest et al.,” as well as Ross and Blesa,” found considerable increase in coronary blood flow and myocardial contractility after intracoronary injection of nicotine. Thie rapid onset of the inotropic response to nicotine and its apparent localization to the area downstream from the point of injection indicated to Ross and Blesa” that catecholamine release or potentiation must

Mechanism of Inhibition of Cholesterol Uptake by the Arterial Wall

Experiments have been described dealing with lipid synthesis and cholesterol uptake in perfused human and pig coronary arteries, rabbit aortas, and with the inhibitory effect of 7-ketocholesterol on cholesterol uptake in these preparations and in rabbits in vivo. Human and pig coronary arteries failed to synthesize cholesterol in vitro. 7-ketocholesterol inhibited cholesterol uptake in human coronary arteries and aortas of pigs and rabbits in vitro and by rabbit aortas in vivo. The inhibitory effect in vivo could only be shown after repeated i.v. injections of 7-ketocholesterol after solubilizing the steroid with bile sale (Na-glycocholate). Although 7-ketocholesterol was absorbed from the G.I. tract, gastric feeding of the bile salt steroid complex was ineffective, probably because of inadequate blood levels of 7-ketocholesterol achieved. The metabolic fate of 7-ketocholesterol and the nature of its effect on cholesterol are discussed. It is not likely that inhibition of HMG-CoA reductase is responsible for the inhibition of cholesterol uptake. The possibility was discussed that both cholesterol and 7-ketocholesterol actively compete for identical and specific binding sites or that an increase in 7-ketocholesterol in plasma leads to an increase in intracellular concentrations of this steroid thus inhibiting cholesterol transfer across the cell membrane. However definite conclusions on the nature of inhibition must await further experimentation.