RESUMO
Changes in endogenous levels of phospholipid arachidonic acid and in its radioactive incorporation can be detected in the rat kidney medulla during maturation. In an effort to explain this phenomenon, the arachidonoyl-CoA synthetase activity in the neonatal (10 days of age) and adult kidney (70-day-old rats) were studied. The neonatal kidney enzyme showed greater affinity, but less capacity than the adult enzyme to incorporate arachidonic acid into the membrane. The apparent Km values were 27.8 and 73.9 microM while the vmax was 3.68 and 15.7 nmol/min/mg protein, for 10 and 70 days of age, respectively. Affinity for ATP was found to be almost 7-fold greater in adults when compared to neonates. The vmax for ATP also increased during development, with values of 1.04 and 2.87 at 10 and 70 days of age, respectively. Affinity for coenzyme A did not vary between the two stages studied, though the vmax increased 10-fold from 10 to 70 days of age. Since arachidonic acid availability is low in the perinatal stage because of its restricted endogenous synthesis, the higher enzyme affinity for this fatty acid at 10 days of age described here, could be of great importance in helping to capture the low but indispensable amount of arachidonic acid present in maternal milk during lactation.
Assuntos
Ácido Araquidônico/metabolismo , Coenzima A Ligases/metabolismo , Medula Renal/enzimologia , Microssomos/enzimologia , Trifosfato de Adenosina/farmacologia , Fatores Etários , Animais , Ácido Araquidônico/análise , Radioisótopos de Carbono , Coenzima A/farmacologia , Estudos de Coortes , Relação Dose-Resposta a Droga , Medula Renal/metabolismo , Cinética , Microssomos/metabolismo , Concentração Osmolar , Ratos , Ratos WistarRESUMO
The biosynthesis of prostaglandins (PGs) from the endogenous and exogenous precursor, arachidonic acid (AA), in renal papilla, medulla and cortex from neonatal to adult rats was investigated. Rat renal papilla and medulla incubated in the presence of [1-14C]AA released radioactive PGE2, PGF2 alpha and PGD2 which increased with age. No radioactive prostaglandins were found in the supernatants of renal cortex at any age studied. The amount of total prostaglandins released from the endogenous precursor also increased from 10 to 70 days of age, PGD2 being the prostaglandin that showed the most important rise. In the cortex, only PGE2 release increased with age. Cyclooxygenase (COX) activity was measured in papillary, medullary and cortical homogenates by using [1-14C]AA as substrate. Papillary and medullary COX activity increased after 10 days of age and continued to rise up to day 30 thereafter remaining unaltered until adulthood. Cortical COX activity was very low and decreased with age. These findings indicate the low capacity of the neonatal rat kidney to synthesize PGs.
Assuntos
Rim/crescimento & desenvolvimento , Rim/metabolismo , Prostaglandinas/biossíntese , Animais , Ácido Araquidônico/metabolismo , Dinoprosta/biossíntese , Dinoprostona/biossíntese , Córtex Renal/metabolismo , Medula Renal/metabolismo , Prostaglandina D2/biossíntese , Prostaglandina-Endoperóxido Sintases/metabolismo , Ratos , Ratos WistarRESUMO
We have studied microsomal phospholipid, cholesterol and protein concentration in rat renal papilla, medulla and cortex during postnatal development, and the relationship between these membranes biochemical parameters and morphological changes. We also determined DNA concentration in each kidney zone. No changes were observed either in papillary microsomal phospholipids, proteins and cholesterol or in DNA concentration from 10-to 70-day-old rats. Medullary microsomal proteins and cholesterol did not change but a significant increase was observed in the microsomal phospholipid concentration during development; in this case, medullary DNA was significantly lower at 70 than at 10 days. In contrast, all biochemical parameters in renal cortex were significantly higher during development except for DNA concentration which suffered a great decrease. These biochemical findings demonstrate that the developmental pattern is different in each zone of the kidney and confirm the fact that the papilla, in newborn rats, is almost fully developed whereas the renal cortex and medulla are immature.
Assuntos
Envelhecimento/metabolismo , Rim/crescimento & desenvolvimento , Rim/metabolismo , Animais , Animais Recém-Nascidos , Colesterol/metabolismo , DNA/metabolismo , Rim/citologia , Microssomos/metabolismo , Índice Mitótico , Fosfolipídeos/metabolismo , Proteínas/metabolismo , Ratos , Ratos Wistar , Distribuição TecidualRESUMO
We have examined the phospholipid content and metabolism in renal papilla, medulla and cortex in 10- to 70-day-old rats. No changes in papillary and medullary phospholipids with an increase in cortical phosphatidylcholine and phosphatidylethanolamine were evident during maturation. Phosphatidylinositol de novo synthesis did not change with age, but a decrease in medullary and cortical phosphatidylcholine and phosphatidylethanolamine was observed. In the three zones [14C]arachidonic acid incorporation into all the phospholipids was the highest at 10 days with a gradual decrease with age, while the [14C]palmitic acid incorporation remained unchanged except for phosphatidylinositol which decreased from 10 to 70 days.
Assuntos
Envelhecimento/metabolismo , Rim/metabolismo , Fosfolipídeos/metabolismo , Animais , Animais Recém-Nascidos , Ácido Araquidônico/metabolismo , Rim/crescimento & desenvolvimento , Metabolismo dos Lipídeos , Masculino , Ácido Palmítico , Ácidos Palmíticos/metabolismo , Ratos , Ratos Wistar , Distribuição TecidualRESUMO
Phospholipid content and metabolism were studied in rat renal papillary, medullary and cortical slices. The highest concentration of phospholipids was found in cortex and the lowest in papilla samples (ratio cortex/medulla, 1.3; cortex/papilla, 3.7). The profile of the various phospholipids was different depending on the zone. The most important difference was the relative concentrations of sphingomyelin (CerPCho) and phosphatidylinositol (PtdIns) with ratios for PtdIns/CerPCho of 5.0, 3.3 and 2.5 in papilla, medulla, and cortex, respectively. In the three zones, PtdIns showed the highest specific activity for [2-14C]glycerol and [1-14C]arachidonic acid incorporation. By contrast, a higher amount of [1-14C]palmitic acid was incorporated into phosphatidylcholine than into any other phospholipid. The various radioactive precursors were only poorly incorporated into phosphatidylethanolamine. No radioactivity was associated with phosphatidylserine. The papilla possesses the most active phospholipid metabolism of all the pathways studied.
Assuntos
Ácidos Graxos/metabolismo , Rim/metabolismo , Fosfolipídeos/metabolismo , Animais , Ácido Araquidônico/metabolismo , Técnicas In Vitro , Rim/química , Córtex Renal/química , Córtex Renal/metabolismo , Medula Renal/química , Medula Renal/metabolismo , Pelve Renal/química , Pelve Renal/metabolismo , Masculino , Ácido Palmítico , Ácidos Palmíticos/metabolismo , Fosfolipídeos/análise , Ratos , Ratos Endogâmicos , Distribuição TecidualRESUMO
In view of the fact that mepacrine (Mp) is usually used as an inhibitor of the endogenous phospholipase A2, and since this enzyme produces the release of arachidonic acid (AA) from membrane phospholipids, we studied the effect of different concentrations of Mp on the mobilization of [1-14C]AA in rat renomedullary phospholipids. During the acylation period, 0.1 mM Mp did not produce any significant change in the incorporation of [1-14C]AA into phosphatidylcholine (PC) and phosphatidylethanolamine (PE), and only a slight increase in phosphatidylinositol (PI). Higher concentrations of Mp (0.5 to 1.0 mM) produced a decrease of radioactivity in PE and PC with an increase in PI. Using prelabeled slices, a dose-dependent decrease in the 14C-radioactivity in PE and PC was observed, with a parallel increase in PI. This effect of Mp persisted even in the presence of a physiological activator of phospholipase A2, bradykinin (BK). No change in the net amount of phospholipids was observed at any of the Mp concentrations used. The results of this study show that Mp, at concentrations generally used to inhibit phospholipase A2, produced a transfer of arachidonic acid from PE and PC to PI, rather than a blockade in the release of AA from membrane phospholipids.
Assuntos
Ácidos Araquidônicos/metabolismo , Fosfatidilinositóis/metabolismo , Quinacrina/farmacologia , Animais , Ácido Araquidônico , Coenzima A/fisiologia , Relação Dose-Resposta a Droga , Técnicas In Vitro , Medula Renal/metabolismo , Fosfolipídeos/análise , Ratos , Ratos EndogâmicosRESUMO
The effect of bradykinin on the mobilization of arachidonic acid was analyzed separately by acylation and degradation. Acylating activity was determined by the incorporation of [14C]arachidonic acid into the phospholipids at different times. Different concentrations of bradykinin had no effect on the phospholipid acylating activities. The degradation of the phospholipids was performed on renal medullary slices prelabeled with [14C]arachidonic acid. Treatment with bradykinin produced an initial degradation of phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, with a concomitant increase in lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylinositol within 5 min of incubation. Phosphatidylcholine-, phosphatidylethanolamine- and phosphatidylinositol increased thereafter and reached the control values after 10 min of incubation. After 30 min, incubation of prelabeled slices with bradykinin produced a significant concentration-dependent increase in the phospholipid-labeling by reutilization of [14C]arachidonic acid. The effect of bradykinin on the phospholipid-labeling was blocked by preincubation with increasing concentrations of dBc AMP. Mepacrine also blocked the bradykinin stimulation in phosphatidylcholine and phosphatidylethanolamine, but had no effect on bradykinin-induced changes in the phosphatidylinositol arachidonic acid moiety.