Abstract
In order to assess neurobehavioral deficit subsequent to early low-level lead-exposure, Wistar-rats were prenatally Pb-exposed via their mothers, neonatally via their dams' milk, and later on via their diet containing lead acetate (745 mg Pb/kg diet). Blood-lead levels (PbB) of dams increased from 24.2–31.2 μg-% during pregnancy and suckling-periods, those of offsprings were 26.6 μg-% at about 16 days of age and 28.5 μg-% at about 190 days of age. Between 100 and 200 days of age 40 male offsprings were subjected to behavioral testing, namely an open field-test and a visual discrimination-learning task. Two learning-tasks of different complexity, i.e. orientation-and size-discrimination, were used. Data of 20 lead-treated animals were compared with those of 20 age-matched controls.
In the open-field test lead-fed animals were significantly more restless than controls; an increase of ambulation, rearing and grooming was observed. In the difficult learning-task, i.e. size discrimination, only the controls did learn the problem, whereas only one of the lead-group did; there was, however, no difference between lead-and control-animals for the easy task, i.e. orientation-discrimination. The observed effects, namely overreaction in the open field and a deficit of visual discrimination learning, may be interpreted in terms of lead-induced CNS-dysfunction. They clearly suggest that the “no-response level” for neurobehavioral damage in the rat, subsequent to early lead-exposure, must be assumed to be lower than 35 μg/100ml.
Zusammenfassung
Zur Erfassung neuropsychologischer Störungen nach ontogenetisch früher Bleiexposition wurde bei männlichen Wistar-Ratten pränatal über deren Mütter, neonatal über die Muttermilch und postnatal über Bleiazetathaltiges Futter (745 mg Pb/kg Futter) chronisch ein erhöhter Blutbleispiegel (PbB) eingestellt. In der Trächtigkeits-und Säugezeit stieg der PbB-Spiegel der Mütter von 24.2 auf 31.2 μg-% an, während derjenige der Nachkommen im Alter von ca. 16 Tagen 26.6 μg-% und im Alter von ca. 190 Tagen 28.5 μg-% betrug. PbB altersgleicher Kontrollen war stets < 6 μg-%. Im Alter zwischen 100 und 200 Tagen wurden 20 Bleitiere und 20 Kontrollen blind verschiedenen Verhaltensprüfungen unterzogen, und zwar einem Open Field-Test und einer visuellen Unterscheidungs-Lernaufgabe. Zwei Lernprobleme unterschiedlicher Schwierigkeit, Richtungs- und Größenunterscheidung, wurden benutzt.
Im Open Field-Test waren die Bleitiere im Vergleich mit den Kontrollen signifikant unruhiger: Lokomotorische Aktivität, Aufrichten und Putzverhalten waren gesteigert. Die schwierige Größenunterscheidung erlernten nur die Kontrollen, während das leichte Problem, nämlich die Richtungsunterscheidung, von Kontroll- und Bleitieren gleich schnell erlernt wurde. Die beobachteten Bleiwirkungen, gesteigerte motorische Unruhe und Lernleistungshemmung, lassen sich als Indikatoren einer funktionellen Hirnschädigung deuten. Sie legen den Schluß nahe, daß die „Wirkschwelle” für neuropsychologische Störungen nach ontogenetisch frühzeitiger Bleieinwirkung bei der Ratte als unterhalb 35 μg/100 ml liegend angenommen werden muß.
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This work was partially supported by “Bundesministerium des Innern (Bonn, Federal Republic of Germany)” and “Commission of the European Communities (Brussels, Belgium)”
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Winneke, G., Brockhaus, A. & Baltissen, R. Neurobehavioral and systemic effects of longterm blood lead-elevation in rats. Arch. Toxicol. 37, 247–263 (1977). https://doi.org/10.1007/BF00330817
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DOI: https://doi.org/10.1007/BF00330817