Yumiko Yamada

Decreased 1,2-diacylglycerol levels in myopathic hamster hearts during the development of heart failure

1,2-Diacylglycerol is believed to play an important role in cellular functions through protein kinase C activation, although its role in cardiac functions remains largely unexplored. We determined the level of 1,2-diacylglycerol and its fatty acid composition in heart tissues from Syrian hamsters with hereditary cardiomyopathy (BIO 14.6 strain) during the development of congestive heart failure from 90 days to 240 days of age. The myopathic hamsters had lower contents of triglyceride and of the major phospholipids, phosphatidylcholine, phosphatidylethanolamine and cardiolipin, in the myocardium when compared to normal hamsters, whereas there was no difference in the cholesterol content. No difference in the myocardial 1,2-diacylglycerol content was observed at 90 days of age. On the other hand, 1,2-diacylglycerol contents in myopathic hearts at 160 and 240 days of age were significantly lower by 21% and 52%, respectively, then in age-matched normal hamsters. The oldest hamsters (240-day-old) showed reduced 1,2-diacylglycerol levels in both groups despite an age-related increase in most lipids. The 1,2-diacylglycerol fatty acid composition profile was found to be different from that of other lipids, and there were several differences in the fatty acid composition of 1,2-diacylglycerol between the two groups at 240 days of age. These results indicate that decreased levels of 1,2-diacylglycerol occur concomitantly with congestive heart failure in the myopathic hamsters.

1,2-diacylglycerol content in thoracic aorta of spontaneously hypertensive rats.

Phosphoinositide metabolism participates in the control of cell calcium homeostasis. Because a notable neutral lipid (1,2-diacylglycerol) is generated from phosphoinositide hydrolysis and is assumed to be a secondary messenger, we determined 1,2-diacylglycerol content and its fatty acid profiles in the thoracic aorta of spontaneously hypertensive rats (SHR) and compared it with those of normotensive Wistar-Kyoto (WKY) rats. After the aorta was exposed to 10(-5) M norepinephrine as a stimulant, 1,2-diacylglycerol content in SHR was significantly higher by 33% than in WKY rats at 4 weeks of age, whereas there was no difference in 1,2-diacylglycerol content between the two strains at 20 weeks of age. Before norepinephrine stimulation, there was no significant difference in 1,2-diacylglycerol level between the two strains at 4 weeks of age. Analysis on a gas chromatograph showed that 1,2-diacylglycerol was composed of similar molecular species of fatty acids in aortas obtained from SHR and WKY rats. On the other hand, the cholesterol content of aortas was higher in SHR than in WKY rats at 20 weeks of age, whereas the difference at 4 weeks was not significant. Phosphatidylcholine, phosphatidylethanolamine, and triglyceride showed no significant difference between the two strains. It is concluded that norepinephrine-induced 1,2-diacylglycerol production increases in the thoracic aorta of SHR before the development of hypertension.

Increased 1,2-diacylglycerol content in myopathic hamster hearts at a prenecrotic stage

1,2-Diacylglycerol (DAG) has been suggested to be a secondary messenger. In this study, we determined the amount of 1,2-DAG in heart tissue from Syrian hamsters with hereditary cardiomyopathy at 30 days (prenecrotic stage) and 90 days of age by thin-layer chromatography with flame ionization detection (TLC-FID). Myocardial triglyceride contents were higher at 30 days of age and lower at 90 days of age compared to the levels in age-matched normal hamsters. Decreases in major species of phospholipids in hearts were observed only at 90 days of age. However, elevated 1,2-DAG content in myopathic hearts was found at 30 days of age, whereas there was no difference between the two groups at 90 days of age. It is suggested that the increase in 1,2-DAG at the prenecrotic stage is involved in the pathogenesis of the cardiomyopathy.

1,2-Diacylglycerol content in myocardium from spontaneously hypertensive rats during the development of hypertension

Summary1,2-Diacylglycerol (DAG) has been considered to play an important role as an activator of protein kinase C in the signal transduction of inositol phospholipid metabolism. To examine the relation of 1,2-DAG in heart tissues to cardiac hypertrophy associated with hypertension, we measured the amount of 1,2-DAG in spontaneously hypertensive rat (SHR) hearts at 4,10 and 20 weeks of age, and in age-matched normotensive Wistar-Kyoto (WKY) rat hearts using thin-layer chromatography with flame ionization detection (TLC-FID). Significant cardiac hypertrophy was found in 4-week-old SHR, while SHR did not yet have significant hypertension. Major phospholipids such as phosphatidylcholine and phosphatidylethanolamine increased from 4 to 20 weeks in the myocardium, but there was no difference between the two strains. The cholesterol levels of 4- and 20-week-old SHR were significantly higher than WKY rats. The 1,2-DAG contents of SHR hearts were significantly higher than WKY rats at 4 weeks. An increase in the RNA contents of SHR hearts were significantly higher than WKY rats at 4 weeks. An increase in the RNA content was also observed in 4-week-old SHR hearts. However, analysis of the fatty acid composition of 1,2-DAG revealed no difference between the two strains. However, there was no significant difference in the 1,2-DAG content or in its fatty acid composition between SHR and WKY rat hearts at 10 and 20 weeks of age. It is suggested that an increase in the 1,2-DAG content of SHR hearts during the early stages appears related to the initiation of cardiac hypertrophy in SHR hearts before developed hypertension.

Altered myocardial acetylcholine and norepinephrine concentrations in right ventricular hypertrophy and failure

SummaryThe progression of cardiac hypertrophy and failure is associated with marked changes in cardiac autonomic innervation, and there are sympathetic-parasympathetic interactions in the regulation of cardiac function. Although the indexes of sympathetic innervation have been found to be depressed with the development of heart failure, those of parasympathetic innervation have not yet been fully investigated. In order to better understand changes in markers of autonomic innervation associated with cardiac hypertrophy and failure, we measured the myocardial acetylcholine (ACh) store as a parasympathetic marker and the norepinephrine (NE) store as a sympathetic marker in pressure-overloaded right ventricular hypertrophy in rats. Two weeks after the injection of monocrotaline, significant right ventricular hypertrophy occurred. Three weeks after, severe right ventricular hypertrophy with no sign of heart failure occurred, and 4 weeks after, overt heart failure developed. In the right heart of monocrotaline rats, NE concentrations tended to increase at 1 week, returned to baseline at 2 weeks, decreased to one-half of the control values at 3 weeks, and then fell to 14% of the controls at 4 weeks. ACh concentrations in the right heart tended to increase at 1 week and exhibited a significant increase (136% and 129% of the controls in the right atrium and ventricle, respectively) at 2 weeks. As with NE, ACh concentrations in the right atrium and ventricle decreased to 76% and 54% of the controls at 3 weeks, and continued to decrease to 22% and 24% of the controls at 4 weeks after monocrotaline. Assessing the net changes, ACh contents (i.e., total mass contained in the whole atrium or ventricle) increased at 2 weeks, although NE contents remained unchanged at the early stages. The NE and ACh contents were maintained until 3 weeks after monocrotaline, whereas both contents were depleted at 4 weeks.Our results suggest that parasympathetic innervation shows a transient increase during progressive hypertrophy due to pressure overload, and that both NE and ACh are depleted with the progression of overt heart failure, although NE and ACh contents in the whole atrium or ventricle are maintained during the compensated state of heart failure.

Quantitative determination of 1,2-diacylglycerol in thoracic aorta of the rat using latroscan TLC/FID: Effect of norepinephrine

This study was undertaken to evaluate the use of the Iatroscan TLC/FID system for quantitating 1,2-diacylglycerol (DG) in the aorta. Cholesteryl acetate was chosen as an internal standard. In order to avoid interference of triglyceride and phospholipids with the separation of the internal standard and 1,2-DG, a stepwise elution of lipids from the silicic acid column was used. The development of Chromarods was done using two solvent systems and a three-step developing technique. Assay and recovery of both 1,2-DG and cholesterol (as compared to cholesteryl acetate) were sufficient to measure changes in the 1,2-DG content in blood vessels. After exposing the thoracic aorta to 10−5 M norepinephrine for 10 min, the 1,2-DG content increased nearly two-fold without significant change in cholesterol content.

Altered Myocardial Neurotransmitter and 1,2-Diacylglycerol Concentrations in Right Ventricular Hypertrophy and Failure in Rats

In order to better understand changes in markers of autonomic innervation associated with cardiac hypertrophy and failure, we measured myocardial acetylcholine (ACh) and norepinephrine (NE) after the injection of monocrotaline (MCT) in rats. We aslo determined 1,2-diacylgcerol (DAG), which is a second messenger activated by these neurotransmitters. At 2 weeks after MCT injection, right ventricular hypertrophy with no sign of heart failure occurred. Acetylcholine and 1,2-DAG concentrations increased by 29% and 55%, respectively, in the right ventricles. Four weeks later, decompensated heart failure was observed. In contrast to the 2-week hearts, the 4-week MCT right ventricles had a significant decrease in NE (-86%), ACh (-76%), and 1,2-DAG (-25%) concentrations, whereas there was no marked change in the left ventricles. These results indicate that parasympathetic innervation shows a transient increase during progressive hypertrophy due to pressure overload, accompanied by an increase in 1,2-DAG, and that NE, ACh, and 1,2-DAG are all depleted with the progression of overt heart failure.

Alteration in 1,2-diacylglycerol level and its fatty acid composition in hearts during the growth of hamsters

SummaryWe measured the amount of 1,2-diacylglyccrol (DAG) and its fatty acid composition in hamster hearts of various ages because 1,2-DAG has been recognized to be onc of the intracellular second messengers. The highest level in 1,2-DAG was detected in 30-day-old hamster hearts. The heart weight increased about 2.5 times between 30 and 90 days of age. Hamster hearts at 90 days of age had 72% of the 1,2-DAG content at 30 days of age. The amount of 1,2-DAG at 240 days of age was a little lower than that in 90-day-old and 160-day-old hamsters, whereas there was no significant increase in heart weight and only a little gain in body weight between 90 and 240 days of age. The analysis of the fatty acid composition of 1,2-DAG showed an increase in the percentage of 18∶0 accompanied by a change in the percentages of other fatty acids with the growth of hamsters. The largest amount of arachidonic acid expressed as 20∶4 (n-6) was found at 30 days of age. On the other hand, triglyceride, cholesterol, and major phospholipid components of hamster hearts increased in accordance with growth. In particular, the increase in triglyceride content was remarkable, indicating that myocardial lipidosis may be induced by aging. These results demonstrate that 1,2-DAG may be involved in the synthesis of protein during heart growth and that the alteration of its fatty acid composition is related to the growth of hamsters.