Lead effects on offspring depend on when mouse mothers were exposed to lead

Target mice were nursed by mothers given lead starting (1) when target mice were born; (2) after conception of target mice, or (3) during the mothers' own pre-weaning age. These target mice are called, respectively, POSTNATAL , GESTATIONAL, and PRE-MATING. Compared to developments in control mice, po stnatal lead slowed brain weight development, lowered asymptotic brain weig ht, decreased DNA per brain somewhat, but had no effect on protein per brai n. Gestational lead similarly slowed brain weight development, lowered asym ptotic brain weight, greatly decreased DNA per brain, but had no effect on protein per brain. In contrast, pre-mating lead significantly increased bra in weight and protein per brain and lowered DNA per brain substantially. Th ese effects of pre-mating lead on brain weight and protein per brain could be due to the effects of lead on developing maternal reproductive systems o r to lead's presence during the rarely studied ovulation-to-fertilization p eriod.