Polyamine Metabolism during the Perinatal Development of the Rabbit Right and Left Ventricle

Abstract

Summary cardiovascular alterations (19) is accom~anied bv increased mvo-The right ventricular (RV) and left ventricular (LV) free wall weights, ornithine decarboxylase (ODC) specific activity and polyamine content were determined in fetal, I-, 2-, 7-, 14, and 21-day-old rabbit hearts. There was a significant increase in the LV free wall weight and a decrease in RV free wall weight between 1-7 days. By day 7 the LV/RV mass ratio doubled and reached a ratio comparable to that seen in adult rabbit hearts. The rate of change in the LV and RV free wall weights were comparable after day 7.There was a significant increase in LV ODC specific activity and a decrease in RV ODC specific activity after birth. The LV ODC specific activity was significantly greater than RV ODC specific activity in both 1 and 2 day old rabbit hearts whereas they were not significantly different in 7 and 14 day old rabbit hearts.The molar content (nmoles/mg wet weight or nmoles/mg protein) of putrescine decreased approximately Ifold fter birth in the RV but increased approximately 2-fold in the LV. The molar content of spermidine and spermine was transiently increased after birth (1 day old) in both RV and LV with approximately a 2-fold increase in spermidine and a 2.5-fold (LV) and 4-fold (RV) increase in spermine content. The increase in LV putrescine content after birth was due, at least in part, to the observed increase in ODC specific activity in the LV free wall. The putrescine/spermidine ratio increased in the LV and decreased in the RV immediately after birth up to day 7. As opposed to the shortlived increase in spermidine and spermine observed in both the RV and the LV free wall, increased ODC specific activity and putrescine accumulation uniquely characterized the preferential growth of the LV between day 1 and 7.cardial cell number as well as increased cell sizi(l0). In the hrst wk of postnatal life an increase in myocyte number accounts for the 2-fold weight difference between the left and right ventricles for developing rats (2).Other differences also have been observed in the rate of microvascular and subcellular organelle maturation of the left versus right ventricle (16,23). From the morphologic features of the neonatal rat heart, LV growth is analogous to combined eccentric and concentric hypertrophy whereas right ventricular growth is analagous to eccentric hypertrophy (2). Presumably the postnatal pressure loading of the newborn LV accelerates its rate of growth with features similar to concentric hypertrophy due to pressure overloading in pathologic states. Thus the postnatally developing heart affords an ideal model for studying the relationship between pressure loading and adaptive myocardial growth because paired comparisons of left and right ventricular parameters are possible.An increase in ornithine decarboxylase (EC. 4.1.1.17) activity, and increased polyamine production by this enzyme, occurs during the initiation of adaptive myocardial growth in the pressure overloaded adult heart. Acute banding experiments have dem...

Postnatal anatomical and functional development of the heart: A species comparison

“…Relative heart weight in the rabbit is reported to decrease from 0.49% at birth to 0.20% in adults (Lee et al, 1975;Boucek, 1982;Fried et al, 1987). Investigators also reported a relative decrease in right ventricular weight from 86% of the left ventricular weight at birth to 54% in adults, with preferential growth of the left ventricle between postnatal days 1 and 7.…”