Exogenous fructose-1,6-bisphosphate is a metabolizable substrate for the isolated normoxic rat heart.

Isolated rat hearts were perfused by the recirculating Langendorff mode under normoxic conditions for 60 min. The Krebs-Ringer buffer was supplemented with 10 mM glucose + 12 IU/l insulin and either [U-14C]-fructose-1,6-bisphosphate (together with 5 mM cold fructose-1,6-bisphosphate) or [U-14C]-fructose (together with 5 mM cold fructose). At the end of perfusion, gaseous 14CO2, 14CO2 trapped in the perfusates, 14C-lactate output and tissue 14C-lactate were assayed in both groups of hearts. Analysis of high-energy compounds, glycogen, lactate, and pyruvate was also performed on the neutralized perchloric acid extracts of the freeze-clamped hearts. Data obtained from the 14C catabolites, originating from the metabolism of the radiolabeled substrates, indicated that the isolated normoxic rat heart metabolizes an 8.5 times higher amount of fructose-1,6-bisphosphate (7.07 mumoles/min/g d.w.) than of fructose (0.83 mumoles/min/g d.w.). CrP, CrP/Cr, glycogen, and total lactate in both tissue and perfusate were significantly higher in fructose-1,6-bisphosphate-perfused hearts. The overall indication is that fructose-1,6-bisphosphate can be taken up in its intact form by myocytes and successively metabolized to support their energy demand, and that its effects on myocardial performance and metabolism should be attributed to the molecule itself rather than to its eventual degradation products.

The oxygen dependence of mitochondrial oxidative phosphorylation and its role in regulation of coronary blood flow.

The oxygen dependence of mitochondrial oxidative phosphorylation measured in isolated cells of cardiac and non-cardiac origin are affected by the metabolic state of the cells. The contribution of oxygen diffusion to the measured P50 value in resting cells is small. In cardiac myocytes, and possibly in the other cells as well, this contribution may become significant near maximal levels of respiration. The influence of cellular energy metabolism on the oxygen dependence of respiration in cardiac myocytes suggests strongly that mitochondrial oxidative phosphorylation in these cells is an oxygen sensor for adjusting coronary vascular tone during normal cardiac function.

Effect of exogenous fructose-1,6-bisphosphate on glycolysis in the isolated perfused rat heart.

To test the mechanism of action of fructose-1,6-bisphosphate (F-1,6-P2), experiments were conducted on isolated perfused rat hearts to measure the glycolytic rate supported by exogenous glucose with simultaneous measurement of oxygen consumption and the release of lactate and pyruvate. Glycolysis was assayed in terms of the release of tritiated water from [5-3H] glucose, a measure of the rate through the aldolase step. It was found that 5 mmol/L F-1,6-P2 reduced the glycolytic rate parallel to the decrease in oxygen consumption. The results suggest that the cardioprotective action of F-1,6-P2 is related to a substrate effect and a decrease in adenosine triphosphate consumption as indicated by a decrease in oxygen consumption in accordance with the recent demonstration of Ca2+ binding by F-1,6-P2.

Cardiovascular risk in young Finns.

This report describes the general outline and progress of a multicentre study on risk factors of coronary heart disease and their determinants in children and adolescents. "Cardiovascular Risk in Young Finns" comprises a cross-sectional study of 3 to 18-year old subjects in 1980, and follow-up studies in 1983 and 1986 in various parts of Finland, and in 1989 in one of the study areas (Turku). The number of participants in 1980 was 3596 (83.1%) of those invited. In 1983 and 1986 83.2% and 77.8% of them, respectively, participated. The study programme has comprised questionnaire data on, for example, general health and living conditions, physical activity, eating habits, smoking, and psychological variables. The physical examination covered height, weight, skinfold thickness, pubertal stages and blood pressure. Blood specimens were obtained to assess concentrations of serum lipids and insulin, and in 1986 also for possible genetic markers of hypercholesterolemia. A 48 hour recall on nutrient intake was obtained from some of the subjects. The follow-up studies have enabled a study of the tracking phenomenon. Other important questions under study include, for example, the possible clustering of risk factors and their determinants. The cohorts studied provide a valuable research basis for the future, with emphasis on enabling a long-term follow-up of the subjects.

Blood pressure in children, adolescents and young adults.

The question of whether blood pressure is one of the main risk factors for cardiovascular diseases in childhood has been evaluated in a Study of Cardiovascular Risk in Young Finns. In the second follow-up study, carried out in 1986, blood pressure was successfully measured in 2500 individuals aged nine to 24 years using a random zero sphygmomanometer. The mean systolic blood pressure in girls rose from 102 mmHg (95th percentile 119 mmHg) at age nine to 116 mmHg (138 mmHg) at age 24 and that in boys from 102 mmHg (95th percentile 121 mmHg) to 128 mmHg (148 mmHg). Diastolic blood pressure was more often measurable using Korotkoff's 5th than the 4th phase. The values observed were similar to those reported by the Second Task Force on Blood Pressure Control in Children, but owing to differences in the methods used to measure blood pressure it cannot be reliably concluded that the blood pressures were similar in the two series. Even in childhood blood pressure measurement is important, and since it changes with the physical size of the child, observations should be compared with normal values such as those reported here. No data are yet available to suggest that children with blood pressure values in the high normal range would benefit from interventions. Thus normal blood pressure value curves should be applied with caution when assessing children.

Obesity in children, adolescents and young adults.

The prevalence of obesity in Finnish children, adolescents and young adults aged three to 24 years was estimated in three surveys performed within the multicentre project, "Cardiovascular Risk in Young Finns" (1980, 1983, 1986). Obesity was defined as either body mass index (weight/height) or skinfold thickness (triceps or subscapular) or both greater than 90th percentiles of age and sex-specific reference data for white children. Its mean prevalences among 9- to 18-year old boys and girls in three surveys (95% confidence limits) were 3.6% (3.1-4.2) and 2.1% (1.7-2.6) as estimated in terms of body mass index and triceps skinfold thickness or 4.3% (3.9-4.9) and 2.6% (2.2-3.1) according to body mass index and subscapular skinfold thickness. Thus the 9- to 18-year old boys were on average more often obese than the girls, but no statistically significant changes in the prevalence of obesity were observed over the period 1980-1986. Body mass index and triceps or subscapular skinfold thicknesses vary in sensitivity as indicators of obesity.

Serum lipids and lipoproteins in children, adolescents and young adults in 1980-1986.

A multicentre study on atherosclerosis precursors in young Finns aged three to 18 years was started in 1980 (3596 subjects) serum lipid concentrations (cholesterol, HDL (high density lipoprotein) cholesterol and triglycerides) were determined (n = 3554) and the apolipoproteins A-I and B measured (n = 1355). Two follow-up studies were carried out in 1983 (n = 2851) and 1986 (n = 2489), when HDL-subfractions (HDL-2-cholesterol and HDL-3-cholesterol) were also determined. Apolipoproteins A-I and B were measured again in 1986 (n = 1202). Serum total cholesterol concentration has fallen by about 1% annually during the 1980's from 5.07 mmol/l (1980) to 4.79 mmol/l (1986) in 9- to 18-year old children and adolescents. Mean values of serum triglycerides have slightly increased during the follow-up from 0.79 mmol/l to 0.84 mmol/l, respectively. In children and young adults (3-24 years) the mean cholesterol concentration was highest at the age of six and lowest during puberty. Concentrations of serum cholesterol, LDL (low density lipoprotein) cholesterol apoprotein B and triglycerides were higher in eastern than in western Finland in 1980 and 1983, but these differences were smaller in 1986, with the exception of serum triglycerides. Both in 1983 and in 1986 HDL-2-cholesterol was lower in the west than in the east, whereas HDL-3-cholesterol was higher in the former. The favourable changes in lipid levels should be reflected in future morbidity and mortality rates from coronary heart disease in Finland.

Regional differences in apolipoprotein E polymorphism in Finland.

Apolipoprotein E (apoE) polymorphism is a genetic determinant of plasma lipid levels and of coronary heart disease risk. We determined apoE phenotypes and plasma lipid levels in 1564 subjects aged three to 18 years, living in five geographical areas of Finland in 1980. ApoE phenotyping was performed directly from plasma by isoelectric focusing and immunoblotting. The serum concentrations of total cholesterol, low density lipoprotein cholesterol and apolipoprotein B varied with apoE phenotype, and there were increases in all three variables (all P less than 0.001) of the order of E2/2 less than E3/2 less than E4/2 less than E3/3 less than E4/3 less than E4/4. These differences were present in all five areas. The mean levels of high density lipoprotein cholesterol, apolipoprotein A-I and triglyceride in the subjects did not differ between the apoE phenotypes or between their areas of residence. The apoE phenotype dependency of serum total and LDL cholesterol remained significant in all five areas during the six year follow-up from 1980 to 1986, when the mean level of serum total cholesterol fell by 5.8% in east (P less than 0.05) and by 4.4% in west Finland (P less than 0.05); the fall was steeper (P less than 0.01) in the east than the west. In all subjects, particularly those in west Finland, the size of the falls of serum total and LDL cholesterol concentrations depended on the apoE phenotype in the order of E3/2 less than E3/3 less than E4/3, but this effect was not seen in the east.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum insulin and other cardiovascular risk indicators in children, adolescents and young adults.

We wanted to determine the levels of fasting serum insulin during growth, the tracking of serum insulin, and the correlation of serum insulin with other coronary heart disease risk indicators in children and young adults. In 1986 2433 subjects, aged nine to 24 were studied, and insulin data were available from the same population in 1980 and 1983. Serum insulin levels showed a peak during puberty in both sexes and the decline in insulin continued after the age of 21. Tracking of serum insulin was only moderate, especially in females and young boys. Serum insulin correlated positively with body mass index, concentrations of serum triglycerides, and blood pressure, and inversely with the concentration of high density lipoprotein cholesterol. High triglycerides, high systolic blood pressure, and low level of high density lipoprotein cholesterol clustered among subjects within the highest insulin quartile. Our results suggest that the insulin resistance phenomenon, caused mainly by obesity and leading to unfavourable levels of other coronary heart disease risk indicators, is already developing in children and young adults. This suggests that preventing obesity in early life is important.

Mechanism of the effect of exogenous fructose 1,6-bisphosphate on myocardial energy metabolism.

The effects of fructose 1,6-bisphosphate (F-1,6-P2) on the isolated Langendorff-perfused heart were studied by monitoring flavoprotein fluorescence, oxygen consumption (MVO2), coronary flow (Fc), systolic intraventricular pressure (Psys), diastolic intraventricular pressure, and contraction frequency. The cellular energy state and cytosolic pH were determined by means of 31P nuclear magnetic resonance. Infusion of 5 mM F-1,6-P2 caused a rapid shift toward reduction in the flavoprotein redox state and initial 50% and 44% decreases in Psys and MVO2, respectively. After a partial recovery, these measures remained 11% and 25% below the basal value. Concomitantly, after an initial transient increase of 13%, Fc remained 17% lower than in the basal state. When the F-1,6-P2 concentration was subsequently increased to 10 mM, psys and MVO2 dropped temporarily to 31% and 29% of the basal value and then remained at 50% and 53%, respectively. Simultaneously, a brief increase was observed in Fc, which then fell 34% below the basal value. Rapid reoxidation of the flavoproteins and increases in MVO2, Psys, and Fc occurred on discontinuation of the F-1,6-P2 infusion. 31P nuclear magnetic resonance during infusions of both 5 and 10 mM F-1,6-P2 revealed a decrease in cytosolic inorganic phosphate and a tendency to increase creatine phosphate, suggesting elevation in the cellular energy state. No changes in intracellular pH occurred as estimated from the chemical shift of the nuclear magnetic resonance of inorganic phosphate. F-1,6-P2 (5 mM and 10 mM) lowered the free Ca2+ concentration in the Krebs-Henseleit bicarbonate buffer (by 32% and 47%, respectively). This probably explains the effects of F-1,6-P2 on mechanical work performance and cellular respiration. A direct metabolic effect also exists, however, because flavoprotein reduction by F-1,6-P2 could be observed in the K(+)-arrested heart, where its effects on MVO2 were minimal. This redox effect may not be caused by changes in free Ca2+ concentration because it could not be reproduced by infusion of EGTA.

Large placental chorioangioma as a cause of congestive heart failure in newborn infants.

Two rare cases of infants born from pregnancies complicated by large placental chorioangiomas are reported. Congestive heart failure occurred early in the neonatal period as the main complication. Chorioangiomas may be diagnosed early in pregnancy by ultrasound examination. Since both maternal and neonatal complications may indicate premature termination of the pregnancy or be conducive to premature birth, repeated ultrasound examinations, including fetal echocardiography and flow measurements, are suggested to determine the optimal time of delivery. Possible pathophysiological mechanisms causing neonatal complications are discussed.

Cellular energetics and the oxygen dependence of respiration in cardiac myocytes isolated from adult rat.

The oxygen dependence of mitochondrial respiration was investigated using suspensions of mitochondria and quiescent ventricular myocytes isolated from adult rat hearts. A new optical method was used to determine oxygen concentration in the suspending media. The P50 for respiration for coupled mitochondria at a high [ATP]/[ADP].[Pi] ratio and oxidizing glutamate/malate was 0.45 +/- 0.03 microM but was increased to 0.57 +/- 0.02 microM by the addition of succinate to the substrate mixture. This value was decreased to less than 0.06 +/- 0.01 microM when the ATP/ADP.Pi ratio was decreased with the uncoupler, carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The P50 value in resting myocytes was 2.23 +/- 0.13 microM at a Vmax of 13.22 +/- 1.38 nmol of O2/g, dry weight/min. During resting conditions, the creatine phosphate/creatine and ATPfree/ADPfree ratios were high in these cells, 6.81 +/- 1.11 and 1131 +/- 185, respectively. Addition of 1 mM Ca2+ to the suspending media increased the P50 by 50% whereas respiration rose by only 10%. Respiratory rate was increased up to about 10-fold by uncoupling the cells, but the P50 increased by less than 3-fold. When these uncoupled cells were inhibited with Amytal to lower the rate of oxygen consumption to that of resting cells, the P50 fell to 1.25 +/- 0.14 microM. Diffusion models indicate that in resting myocytes, the oxygen concentration difference from sarcolemma to cell core was approximately 1.84 microM with an additional difference of about 0.27 microM attributed to the unstirred layer of media surrounding each cell. The intracellular oxygen diffusivity coefficient in myocytes was calculated to be 0.30 x 10(-5) cm2/s. The results show that the oxygen dependence of respiration is modulated by the cellular metabolic state. At near maximal levels of respiration or on recovery from hypoxic episodes, oxygen diffusion may become an important determinant of the oxygen dependence of myocardial respiration.

Two cases of large placental chorioangioma with fetal and neonatal complications.

Two cases of infants born from pregnancies complicated by large placental chorioangiomas causing congestive heart failure in the neonate as the main complication are presented. Chorioangiomas may be diagnosed early in pregnancy by ultrasound examination. Since both their maternal and their neonatal complications may indicate premature termination of the pregnancy or be conducive to premature birth, repeated ultrasound examinations, including fetal echocardiography, are suggested in order to optimize the timing of the delivery.

Regulation of coronary blood flow.

Regulation of coronary blood flow (CBF) is a complex process in which many neural, mechanical, myogenic and metabolic factors are involved and is largely controlled by local factors. Our recent results suggest that CBF and oxygen delivery to cardiac tissue is regulated according to the actual needs of the tissue, determined by oxygen consumption in the mitochondrial respiratory chain, controlled by the energy state of the cell. Several substances have been proposed to serve as messengers between the cardiac myocyte and the vascular smooth muscle cells. Abundant evidence has been accumulated showing that adenosine is an important regulator of CBF, its effects being thought to be mediated by binding to specific external or internal surface receptors, with regulatory link to adenylate cyclase. There is also evidence that adenosine formation takes place intracellularly, predominantly via a cytosolic 5'-nucleotidase. The intracellular level of adenosine is thought to be under delicate control by adenosine producing and metabolizing enzymes. Several arachidonic acid metabolites, especially prostacyclin, are also involved in the regulation of coronary circulation. The physiological significance of atrial natriuretic factor, which also seems to regulate CBF, cannot be established at this stage.

The effect of cholinergic agonists on coronary flow rate and oxygen consumption in isolated perfused rat heart.

The metabolic and circulatory consequences of activation of the muscarinic receptor(s) were investigated by local administration of acetylcholine and its three analogues (bethanechol, carbachol and methacholine) into beating and KCl-arrested perfused rat hearts. Acetylcholine and the three other choline esters caused vasoconstriction in both types of preparations and this vasoconstriction was accompanied by a decrease in oxygen consumption. In most cases the dose-response curves were biphasic and changes in coronary flow paralleled those in oxygen consumption. Both phenomena were abolished by administration of atropine and either removal of calcium or infusion of verapamil but were unaffected by addition of the adrenergic alpha-blocker, prazosin, and the adrenergic beta-blocker, propranolol. Infusions of low concentrations of the cholinergic agonists were accompanied by increases in the myocardial phosphorylation state ratio [( ATP]free/[ADP]free[Pi]) which correlated with the simultaneous decreases in oxygen consumption and coronary flow. It is suggested that muscarinic receptors responsible for vasoconstriction in perfused rat heart are located not only on coronary vessels but also on the cardiac muscle cells. Activation of the former receptors induces vasoconstriction by direct action on the vascular smooth muscle while activation of the latter receptors induces vasoconstriction indirectly by decreasing cardiac work and increasing the myocardial [ATP]free/[ADP]free[Pi] ratio. The results also show that stimulation of muscarinic receptor(s) and the consequent metabolic and vasoregulatory responses are coupled to calcium movements.

Subcellular origin of the surface fluorescence of reduced nicotinamide nucleotides in the isolated perfused rat heart.

Surface fluorometric measurements and indicator metabolite determinations in the isolated perfused rat heart showed that the NADH + NADPH fluorescence of the intact tissue originates largely from the mitochondria. The redox potential of the lactate dehydrogenase system calculated from the endogenous lactate/pyruvate ratios was closely similar to that of the glycerol-3-phosphate dehydrogenase system calculated from the concentrations of glycerol-3-phosphate and dihydroxyacetone phosphate in the tissue. Thus, in contrast to the liver, the cytosolic redox state of the NADH/NAD+ system in isolated perfused heart oxidizing external glucose or fatty acid is not amenable to optical monitoring, but can be assessed from the state of the lactate dehydrogenase or glycerol-3-phosphate dehydrogenase systems.

Mitochondrial oxidative phosphorylation: tissue oxygen sensor for regulation of coronary flow.

The observation that mitochondrial oxidative phosphorylation in vivo is dependent on oxygen tension throughout the physiological range (Wilson et al., 1979a , 1979b ) has made this metabolic pathway the most probable candidate for the tissue oxygen sensor in the regulation of local blood flow. We have utilized the oxygen dependent regulatory system for coronary blood flow to examine this possibility. Alterations in coronary flow were induced by: 1. Varied work load; 2. Infusion of Amytal (an inhibitor of mitochondrial respiration); 3. Infusion of DNP; 4. Hypoxia. Increased work load caused increased coronary flow with no decrease in effluent oxygen tension while Amytal infusion and hypoxia caused vasodilation with increased and decreased O2 tension respectively. This indicates that oxygen tension per se cannot be responsible for the observed vasodilation. Tissue energy metabolism was evaluated by measuring metabolite levels in hearts which were freeze-clamped in each state of perfusion. In all four methods of vasodilation, a decrease in cellular energy state ratio ([ATP]f/[ADP]f[Pi]) expressed as the calculated ratio of free adenine nucleotides, was observed for conditions which increased flow. Systematic variation of work load, Amytal or DNP concentration resulted in quantitatively the same correlation between tissue [ATP]f/[ADP]f[Pi] and coronary flow. It is concluded that mitochondrial oxidative phosphorylation is the oxygen sensor for the regulation of coronary blood flow by tissue oxygen tension. Infusion of adenosine, a known coronary vasodilator, induced vasodilation which was completely blocked by theophylline.(ABSTRACT TRUNCATED AT 250 WORDS)

Tricarboxylic acid cycle metabolites during ischemia in isolated perfused rat heart.

Isolated rat hearts were, after a retrograde perfusion by the Langendorff procedure, rendered ischemic by lowering the aortic pressure to zero. The rate of proteolysis and temporal patterns of the changes in the concentrations of the metabolites of the tricarboxylic acid cycle, related amino acids, ammonia, and breakdown products of the adenine nucleotides were determined. The most significant change in the amino acid metabolism was a decrease of the proteolysis to one-tenth and a large accumulation of alanine, which was almost stoichiometric to the degradation of aspartate plus asparagine. The accumulation of malate and succinate was small compared with the metabolic net fluxes of aspartate and alanine. The metabolic balance sheet suggests that aspartate was converted to alanine. A prerequisite for this would be a feed in of carbon of aspartate to the tricarboxylic acid cycle as oxalacetate, reversal of the malate dehydrogenase, and production of pyruvate by the malic enzyme reaction. Alanine accumulating during ischemia is not glycolytic in origin but occurs through a concerted operation of anaplerotic reactions and tricarboxylic acid cycle metabolite disposal. The data also suggest that the potentially energy-yielding reduction of fumarate to succinate is not significant in the ischemic myocardium.