Time and level of perinatal lead exposure for development of norepinephrine cardiotoxicity.

Neonatal lead exposure produces an enhanced susceptibility of the adult rat heart to the arrhythmogenic effects of norepinephrine. The present study examines the relationship of time and level of exposure to the extent of cardiac abnormality produced. The results indicate that the level of lead exposure required to produce norepinephrine cardiotoxicity without overt growth retardation is quite narrow, and lead must be present during the first ten days of life to cause these effects on the heart. A critical concentration of lead achieved during the early time period after birth appears necessary for the production of this cardiac abnormality, suggesting that lead interferes with neonatal cardiac and/or autonomic development.