Maternal impacts of pre-conceptional glyphosate exposure

Maternal glyphosate (GLY) impacts remain unclear despite associations between urinary GLY and birth outcomes. Whether maternal pre-conceptional GLY exposure would have phenotypic and molecular impacts in the dam and offspring was tested. Female C57BL6 mice (6 wk) were exposed to saline (CT; n = 20) or GLY (2 mg/kg; n = 20) per os five d per week for 20 wk. Females were housed with males and on gestation day (GD) 14, divided into: CT non-pregnant (CNP), CT pregnant (CP), GLY non-pregnant (GNP), GLY pregnant (GP). Another cohort (CT; n = 10 or GLY; n = 10) completed three pregnancy rounds and pregnancy index (PI), number of pups per litter and pups surviving to postnatal day (PND) 5 calculated. The PI in GLY mice was higher in breeding rounds 1 and 2, but lower in round 3. Pregnancy increased (P ≤ 0.1) GD14 liver and ovary weight. Spleen weight was increased (P < 0.05) in GP relative to GNP mice. No offspring phenotypic impacts were observed. Approximately six months after cessation of exposure, secondary follicle number was reduced (P < 0.05) by pre-conceptional GLY exposure. The ovarian proteome analyzed by LC-MS/MS was altered (P < 0.05) by pregnancy (49 increased, 43 decreased) and GLY exposure (non-pregnant: 75 increased, 22 decreased, pregnant: 27 increased, 29 decreased; aged dams: 60 increased, 98 decreased) with several histone proteins being altered. These findings support ovarian transient and persistent impacts of GLY exposure and identify pathways as potential modes of action.