Effect of lactate infusion on myocardial FFA metabolism in diabetic dogs.

The effect of elevated arterial lactate concentration on myocardial free fatty acid (FAA), acetoacetate (AcAc), and beta-hydroxybutyrate (beta-OHB) uptake was studied in alloxan-diabetic dogs under control conditions and following the constant infusion of Na-L-(+)-lactate. Only minor changes in hemodynamic parameters were observed. During lactate infusion, arterial lactate increased and FFA, AcAc, and beta-OHB decreased. The extraction ratio and myocardial uptake of both AcAc and beta-OHB diminished. No significant change of myocardial FFA oxidation was noted. While myocardial lactate uptake was very small under control conditions, it increased considerably during the infusion of lactate. The fraction of myocardial CO2 production derived from FFA oxidation was unchanged during lactate infusion, while the fraction derived from ketone bodies decreased and that derived from lactate increased. Thus, during hyperlactacidemia a larger fraction of myocardial substrate was derived from lactate and a smaller fraction from ketone bodies than were derived under control conditions.     

The cardiac apex and its superficial blood supply

Summary The cardiac apex was defined and 3 types were presented: the anatomical apex, the base of which was established at the incisura apicis cordis; the amplified anatomical apex, twice the volume of the preceding; and the geometric apex, the distal third of the ventricles. These types of cardiac apex were studied in connection with the superficial branches of the coronary series at their level. The investigation was conducted on 81 normal hearts (56 males and 25 females) of 60 Caucasian and 21 non-Caucasian individuals. The arteries were injected with colored gelatine mixed with a radiopaque substance. The number of branches decreased from the geometric (the largest type) to the anatomical apex (the smallest): 27 on the surface of the geometric apex, 14 on the surface of the amplified anatomical apex, and 7 on the surface of the anatomical apex. The sternocostal aspect had a higher number of superficial branches than the diaphragmatic aspect in all types of cardiac apex. Sexual differences were found in the incidence of the r posterior ventriculi sinistri intermedius on the amplified anatomical apex as it was more frequent in females than in males. In the geometric apex there were 3 branches also more frequent in females: r anterior ventriculi sinistri inferior, r posterior ventriculi sinistri lateralis I, and r posterior ventriculi sinistri lateralis IV.

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L'apex du cœur et sa vascularisation superficielle

Résumé Cette étude comporte un essai de définition de l'apex du cœur et une présentation d'une classification en 3 types: l'apex ? anatomique ?, dont la base est délimitée par l'incisure de l'apex du cœur, l'apex ? anatomique élargi ?, occupant le double volume du précédent et l'apex ? géométrique ?, occupant le tiers distal des ventricules. La vascularisation de ces 3 types d'apex cardiaque par les branches superficielles des artères coronaires, est précisé. Ce travail a été effectué sur 81 cœurs normaux (56 hommes et 25 femmes) dont 60 Caucasiens et 21 non Caucasiens. Les artères ont été injectées avec un mélange de gélatine colorée et de substance radio-opaque. Le nombre des rameaux artériels va en décroissant depuis le type géométrique (le plus volumineux) jusqu'à l'apex anatomique (le plus petit): 27 sont retrouvés à la surface de l'apex géométrique, 14 à la surface de l'apex anatomique élargi et 7 seulement au niveau de l'apex anatomique. Des différences selon le sexe ont été observées au niveau du rameau postérieur du ventricule gauche qui est retrouvé plus souvent chez les hommes que chez les femmes pour les apex anatomiques élargis. Pour les apex géométriques, 3 branches sont également plus fréquentes chez les femmes: le rameau antérieur et inférieur du ventricule gauche, les branches I et IV du rameau postérieur et latéral du ventricule gauche.

     

The effect of hypercapnia on myocardial blood flow and metabolism

1. In closed-chest dogs anaesthetized with trichlorethylene, the inhalation of carbon dioxide sufficient to increase the arterial P(CO2) from 40 to about 100 mm Hg, increased myocardial blood flow (measured using a (133)Xe clearance technique) and right atrial pressure. There were no consistent changes in mean arterial blood pressure, heart rate or cardiac output.2. The effect of hypercapnia on myocardial blood flow was not influenced by the previous administration of atropine and propranolol or of bretylium. It can be concluded, therefore, that the elevated arterial P(CO2) has a direct vasodilator effect on the myocardial microcirculation.3. During hypercapnia the coronary sinus P(O2) was increased and the coronary arteriovenous oxygen content difference, and calculated myocardial oxygen consumption, reduced. It is suggested that this latter effect may be the result of myocardial depression produced by the decrease in arterial blood pH.4. There was no evidence of myocardial glucose uptake either before or during hypercapnia. The myocardial extraction of lactate and pyruvate at rest varied between 0 and 55%. During acute hypercapnia the extraction of lactate usually fell.5. When the arterial P(CO2) was maintained at 100 mm Hg for a period of 1 hr the effects on myocardial blood flow and on oxygen consumption were not sustained.6. Stepwise increments and decrements in arterial P(CO2) of 10-20 mm Hg produced corresponding increases and decreases in myocardial blood flow and demonstrated that changes in arterial P(CO2) of 20-30 mm Hg can markedly affect blood flow in the myocardium.     

Sex differences in myocardial metabolism and cardiac function: an emerging concept

There is substantial evidence that there are dramatic sex-related differences in the incidence of cardiovascular disease, apparently related to the presence of steroid hormones. This is supported by the discovery of steroid hormone receptors in the heart and vasculature. More controversial is the area of sex-related differences in cardiac metabolism and function. A number of human and animal studies have demonstrated that estrogen and testosterone have cardiac metabolic effects. Additionally, research shows females have higher heart rates and various indices of function, including cardiac output and stroke volume, compared with males. However, some controversy exists, as other studies report that function in isolated muscle preparations is lower in females versus males. The reasons for these differences may reflect effects of sex hormones that are dependent on the conditions being studied. Cardiac function is reduced in postmenopausal females, suggesting that female sex hormones, specifically estrogen and progesterone, influence cardiac function. Apart from its well-documented vasodilatory effects, estrogen has also been shown to have negative inotropic effects and to reduce Ca²⁺ transients in cardiomyocytes. Similar results have been found for progesterone. Several studies show that testosterone administration appears to increase cardiac performance, while others show that it increases the stiffness of the ventricle due to increased collagen synthesis, thereby reducing diastolic performance. This review will discuss current evidence suggesting sex-related differences in cardiac metabolism and its energetics and function and will present the potential role of the principal sex steroid hormones.     

Relationship between blood supply to myocardial segments and their contractility in dogs with intact and ischemic myocardium

In dogs with an intact heart, intravenously administered dipyridamole increased the contractility of a myocardial segment 30–80% and the volume rate of coronary blood flow 142±14%. Dipyridamole administered to dogs before their coronary artery was occluded for 3 min did not decrease the contractility of the ischemia-affected myocardial segment. In dipyridamole-treated dogs with well-developed collaterals, blood was redistributed to the intact zone and the blood flow in the vein draining the ischemic zone increased by 168±17%. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 11, pp. 473–477, November, 1995 Presented by G. N. Kryzhanovskii, Member of the Russian Academy of Medical Sciences     

Modification of regional myocardial performance caused by blood withdrawal and infusion in acute ischaemic canine heart

The effect of changes in preload on regional myocardial motion in acute ischaemia was examined by miniature ultrasonic gauges after left anterior descending coronary artery occlusion in eight open chest dogs with the pericardium preserved. Left ventricular end-diastolic pressure was varied by blood withdrawal and infusion. When preload changed, isovolumetric shortening in the non-ischaemic region was inversely related to that in the ischaemic region. When preload decreased, stroke volume decreased and was accompanied by a decrease in end-diastolic length and ejection shortening in the non-ischaemic region together with an increase in isovolumetric bulging in the ischaemic region. When preload increased, these variables changed in opposite directions. These results indicate that in acute ischaemia: (1) changes in isovolumetric shortening in the non-ischaemic and ischaemic regions were related with each other when the level of volume expansion varied, and suggest that; (2) stroke volume is affected by end-diastolic length, ejection shortening in the non-ischaemic region and isovolumetric bulging in the ischemic region.     

缺血后心肌的代谢、电活动、心肌血流量和形态学改变相关性的分析

以20只麻醉犬,急性闭塞左前降冠状动脉造成局部心肌缺血,对不同时间和不同部位的心肌血流量、心肌代谢和形态学共10项指标作了测定,并用微机处理数据,进行多元回归相关性分析。结果提供了各指标间的相关系数,10项心肌缺血后的改变相互间相关性表明,按冠状动脉解剖学为基础对心肌分区,各区内不同时间呈现高度相关性的指标之特征。本工作可以表明,所有缺血性改变之间普遍存在着相关性,不同时间和不同部位其高度相关性有异。     

Saline-induced natriuresis and renal blood flow in conscious dogs: effects of sodium infusion rate and concentration

AIM: This study focused on static and dynamic changes in total renal blood flow (RBF) during volume expansion and tested whether a change in RBF characteristics is a necessary effector mechanism in saline-induced natriuresis. METHODS: The aortic flow subtraction technique was used to measure RBF continuously. Identical amounts of NaCl (2.4 mmol kg(-1)) were given as slow isotonic (Iso, 120 min), slow hypertonic (Hyper, 120 min), and rapid isotonic loads (IsoRapid, 30 min). RESULTS: During Iso and IsoRapid, arterial blood pressure increased slightly (6-7 mmHg), and during Hyper it remained unchanged. Iso and Hyper increased sodium excretion (4 +/- 1 to 57 +/- 27 and 10 +/- 4 to 79 +/- 28 micromol min(-1), respectively) and decreased plasma renin activity (by 38% and 29%), angiotensin II (by 56% and 58%) and aldosterone (by 47% and 65%), while RBF remained unchanged. IsoRapid caused a similar increase in sodium excretion (to 72 +/- 19 micromol min(-1)), a similar decrease in renin system activity, but a 15% elevation of RBF (282 +/- 22 to 324 +/- 35 mL min(-1)). Selected frequency domain parameters of RBF autoregulation did not change in response to any load. CONCLUSIONS: In response to slow saline loading simulating daily sodium intake, the rate of sodium excretion may increase 10-20-fold without any change in mean arterial blood pressure or in RBF. Regulatory responses to changes in total body NaCl levels appears, therefore, to be mediated primarily by neurohumoral mechanisms and may occur independent of changes in arterial pressure or RBF.     

The effects of l-norepinephrine on myocardial zonal lesions in dogs in hemorrhagic shock

Intravenous l-norepinephrine was given to dogs in hemorrhagic shock to determine the effect on myocardial zonal lesions which are characteristically seen in hypovolemic shock. Zonal lesions produced by hemorrhagic shock in drug-treated and nondrug-treated groups were quantitatively compared both at the light microscopic and ultrastructural levels. A significantly greater percentage of myocardium was found to be involved with zonal lesions in animals treated with l-norepinephrine following shock as compared to that found in nondrug-treated animals. The effect was greater for the right ventricle than for the left ventricle. The average size of zonal lesions was slightly smaller in the drug-treated group, indicating that there must have been a greater total number of zonal lesions produced in the treated group. Zonal lesions were not present in "sham shock" animals nor in animals given l-norepinephrine alone. The results indicate that the treatment of hemorrhagic shock with l-norepinephrine can be anatomically deleterious to the heart.