The purpose of this study was to compare a pattern of 7 enzymes of energy-supplying metabolism in atrial and ventricular myocardium in some mammalian species. Tissue samples of right and left atria and ventricles were obtained from adult male rats, guinea-pigs, rabbits, dogs and pigs. The results clearly demonstrate significant differences in enzyme activities between the atria and ventricles in all these species. In the atria the activity of enzymes connected with aerobic and lactate metabolism (hydroxyacyl-CoA-dehydrogenase, citrate synthase, malate dehydrogenase and lactate dehydrogenase) was markedly lower than in ventricles. On the other hand, in rats, dogs and pigs glucose phosphorylation capacity (hexokinase) was approximately the same in atrial tissue as in ventricles. Right-to-left metabolic differences were much less expressed; conspicuous was only the higher activity of hydroxyacyl-CoA-dehydrogenase in the left atria and ventricles of guinea-pigs and rabbits indicating higher fatty acid utilization capacity in the left heart.
A patent ductus arteriosus (DA) was maintained in newborn rats (Wistar strain) by administering prostaglandin E2 (PG E2) in doses of 15 /ig.kg'1 at 30 min intervals up to 300 min after birth. In the control animals, the DA was functionally closed 300 min after birth. The lumen was blocked by clustered endothelial cells at various stages of degeneration. Elastic membranes of the media had disintegrated into irregular fragments and the smooth muscle cells were contracted. Cytoplasm excrescences formed on their surface as a result of contraction protruded as hernias into adjacent muscle cells and into endothelial cells. The smooth muscle cells degenerated. The administration of PG E2 inhibited contraction of the smooth muscle cells and so also the development of degenerative changes; 300 min after birth the DA was fully patent, the elastic membranes were structurally intact, regularly organized and continuous. The smooth muscle cells had the character of synthesizing cells with richly developed granular endoplasmic reticulum. The intima and its endothelial lining were likewise free from structural changes. The ultrastructural image of the wall of the DA correspondent to the state 10 min after birth, when the DA was fully patent. The administration of PG E2 did not induce any ultrastructural changes indicative of injury to the wall of the DA.
Samples of myocardial tissue were obtained during surgical intervention from children operated for different types of congenital heart disease (tetralogy of Fallot, ventricular and atrial septal defect). Sarcoplasmic, contractile and collagenous proteins were isolated by stepwise extraction from the both right ventricular and atrial musculature. It has been found that: a) the concentration of contractile proteins is significantly higher in the ventricles, b) the concentration of collagenous proteins is significantly higher in the atrium, c) the concentration of sarcoplasmic proteins was not different, d) in children with chronic hypoxia the above atrio-ventricular differences persisted. Moreover, the proportion of the soluble collagenous fraction in the atria was significantly increased.