Quantitative measurement of water consumption patterns in lactating female and neonatal Fischer 344 rats employing [14C]methylcellulose.
Lactating female and neonatal Fischer 344 rats were given water containing [14C]methylcellulose, a nonabsorbed marker, over a 24-hr interval on Days 13, 15, 18, 21, 24, and 27 postpartum. The amount of water consumed was calculated based on the 14C activity recovered in the feces and gastrointestinal tract. Maternal water consumption during the first 28 days postpartum, when expressed as g/kg/day, averaged 2.5 times the level consumed by nonlactating female rats. Maternal water consumption peaked on Day 21 postpartum at 3.3 times the level measured in nonlactating female rats of comparable age. Neonatal water consumption began on Day 18 postpartum and by Day 28 postpartum was 1.9 times the level observed in nonlactating females. Average neonatal water consumption between Days 21 and 28 postpartum was 1.3 times the level for nonlactating female rats. These data indicate that when the test material is administered via the drinking water the dose levels received by the maternal and neonatal rats have been routinely underestimated, and that conclusions concerning the dose-response relationship or increased sensitivity during this period must be tempered by these results.
Kirk
H D
HD
Health and Environmental Sciences, Dow Chemical, Midland, Michigan 48674.
Nolan
R J
RJ
D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001835:Body Weight / Q000187:drug effects; D004326:Drinking / Q000187:drug effects*; D005260:Female; D007774:Lactation; D008297:Male; D008747:Methylcellulose / Q000633:toxicity*; D011247:Pregnancy; D051381:Rats; D011916:Rats, Inbred F344
D008747:Methylcellulose