Biochemical Testing After Pheochromocytoma Removal: How Early?

Pheochromocytomas are catecholamine-producing tumors with typical clinical presentation. Tumor resection is considered as an appropriate treatment strategy. Due to its unpredictable clinical behavior, biochemical testing is mandatory to confirm the success of tumor removal after surgery. The aim of the study was to investigate the feasibility of a shorter interval of postoperative testing (earlier than the recommended 2-4 weeks according to recently published Guidelines). We investigated 81 patients with pheochromocytoma before and after surgery. Postoperative examination was performed of stable subjects after their transport from the surgical to the internal ward (7.1±2.2 days after surgery). Plasma metanephrines were used for the diagnosis of pheochromocytoma and confirmation of successful tumor removal. All subjects with pheochromocytoma had markedly elevated plasma metanephrines before surgery. No correlation between postoperative interval (the shortest being 3 days) and plasma metanephrine levels was found. Postoperative plasma metanephrine levels did not differ significantly from those taken at the one-year follow-up. In conclusion, we have shown that early postoperative diagnostic workup of subjects with pheochromocytoma is possible and may thus simplify early postoperative management of this clinical condition.

Transient upregulation of protein kinase C in pressure-overloaded neonatal rat myocardium.

Protein kinase C (PKC) appears to play a significant role in the signal transduction of cardiac growth and development. The aim of this study was to determine changes in the total PKC activity and the expression of PKC isoforms alpha, delta and epsilon in the rat heart that was affected by pressure overload imposed at postnatal day (d) 2. Three groups of Wistar rats were employed for the experiment: rats submitted to the abdominal aortic constriction (AC), sham-operated controls (SO) and intact controls. Animals were sacrificed at d2, d3, d5 and d10. The total PKC activity was measured by the incorporation of (32)P into histone IIIS and the expression of PKC was analyzed by immunoblotting in the homogenate of the left ventricular myocardium and in the cytosolic, membrane-enriched (10(5) g) and nuclear-cytoskeletal-myofilament-enriched (10(3) g) fractions. We observed the significant transient increase in both the total PKC activity and the expression of all isoforms at d5 (the third day after the operation) in the cardiac homogenate of AC rats as compared with SO animals. Aortic constriction did not significantly affect the distribution of activity and isoform abundance among individual cellular fractions except for PKCdelta, which increased significantly at d10 in the cytosolic fraction at the expense of the membrane-enriched fraction. It is concluded that PKCalpha, PKCdelta and PKCepsilon undergo transient upregulation associated with the accelerated cardiac growth induced by pressure overload imposed in the very early postnatal period.

Myocardial phospholipid remodeling under different types of load imposed during early postnatal development.

Normal increase in hemodynamic load during early postnatal life is associated with heart growth and maturation of membrane structures that is accompanied by remodeling of membrane protein and lipid components. This review describes remodeling of phospholipids (PL) in rat myocardium during normal postnatal development and during accelerated cardiac growth induced by additional workload (aorta constriction, chronic hypoxia and hyperthyroidism) imposed on the heart early after birth. Normal physiological load after birth stimulates the development of membrane structures and synthesis of PL. While hyperthyroidism accelerates these processes, pressure overload has an inhibitory effect. These changes primarily influence the maturation of mitochondrial membranes as cardiolipin is one of the most affected PL species. The most sensitive part of PL structure in their remodeling process are PL acyl chains, particularly polyunsaturated fatty acids that are the key components determining the basic physicochemical properties of the membrane bilayer and thus the function of membrane-bound proteins and membrane-derived signaling lipid molecules. It is evident that PL remodeling may significantly influence both normal and pathological postnatal development of myocardium.

Protein kinase C activity and isoform expression during early postnatal development of rat myocardium.

Total protein kinase C (PKC) activity, its isoform expression, and concentration and fatty acid (FA) composition of diacylglycerol (DAG) were determined in the left ventricular myocardium of the rat during early postnatal development (d 2, 3, 5, 7, and 10). PKC activity measured by the incorporation of 32P into histone IIIS decreased between d 2 and 10 in the homogenate as well as in cytosolic, membrane (100,000 g), and nuclear-cytoskeletal-myofilament fractions (1000 g). Likewise, the expression of PKC isoforms (alpha, delta, and epsilon) determined by immunoblotting generally declined during the period analyzed, although with a variable pattern. In the membrane and nuclear cytoskeletal myofilament fractions, PKCdelta and PKCepsilon expression decreased markedly by d 3, returning to or close to the d 2 level immediately on d 5. PKCalpha expression in the membrane fraction remained almost unchanged by d 7, declining thereafter. PKCdelta and PKCepsilon were associated predominantly with particulate fractions, whereas PKCalpha was more abundant in the cytosolic fraction. DAG concentration exhibited a significant decline by d 5, consistent with the decrease in maximal PKC activity. The unsaturation index of FA in DAG tended to decrease on d 3 owing to the lowered proportion of all polyunsaturated FA of n-6 and n-3 series. These results demonstrate that the developmental decrease in PKC activity and expression in the rat myocardium is not linear and that subcellular localization of the enzyme exhibits isoform-specific day-by-day changes during the early postnatal period. These changes are compatible with the view that PKC signaling may be involved in the control of a rapid switch of myocardial growth pattern during the first week of life.

Phospholipid composition of myocardium in children with normoxemic and hypoxemic congenital heart diseases.

Samples of myocardial tissue were obtained during cardiac surgery from children operated for different types of normoxemic and hypoxemic congenital heart diseases. The phospholipid composition was analyzed by thin layer chromatography. The concentration of total phospholipids (PL), phosphatidylcholine and phosphatidylethanolamine (PE) was found lower in atrial tissue of both normoxemic and hypoxemic groups in comparison with the ventricles. When comparing the difference between hypoxemic and normoxemic defects, hypoxemia was found to increase the concentration of total PL, PE and phosphatidylserine in ventricles and total PL and PE in the atria. The increased level of particular phospholipid species may represent adaptive mechanisms to hypoxemia in children with congenital heart diseases.