Na(+) K(+) ATPase activity in synaptosomes and myelin of developing control and intra-uterine growth retarded rats: effects of lead and serotonin.
An intrauterine growth retarded (IUGR) model based on restriction of blood supply to fetuses at 17 days of pregnancy in rats was studied. We investigated in vitro the effects of lead on Na(+)K(+) ATPase activity in synaptosomes and myelin of IUGR and control rats from 6 to 60 days after birth. In both groups an age-dependent effects existed in synaptosomes for the lowest doses of lead. The experimental group tended to be more sensitive to the metal than the control group and the Na(+)K(+)ATPase activity was less inhibited in the younger rats as compared to mature rats. Serotonin (5-HT) added to the subcellular preparations produced different changes in Na(+)K(+)ATPase activity. In synaptosomes, 5-HT stimulated the enzyme activity in a dose-related manner and apparently reversed the inhibiton induced by lead up to 22 days after birth in the control group. This action was less marked in the IUGR group. In myelin fractions, the Na(+)K(+)ATPase activity was inhibited by lead in both groups but the "protective effect of monoamines" was never observed. The Na(+)K(+) ATPase activity was modulated by monoamines in synaptosomes and not in myelin, perhaps through a mechanism involving soluble factor(s).
Chanez
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INSERM Unité 29, Hôpital Port-Royal, 123 Boulevard de Port-Royal, 75014 Paris, France.
Barone
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Flexor
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Bourre
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