title: Tritiated water as a measure of body water in immature rats growing at different rates.
abstract: Rats were reared from birth in litters of 4, 10, and 16 to achieve different growth rates. Pups in the litters of 16 had no access to rat chow until days 21-28, when chow was made available to one of the litters to induce catch-up growth. Total body water was estimated by tritiated water (TBWHTO) on days 7, 14, 21, and 28 and then calculated from desiccation (TBWdes). TBWHTO was consistently larger than TBWdes for all groups. Differences were 10.9-16.9% on day 7 and 3.7-6.4% on day 28. On day 28, percent difference was higher in the slower-growing than the faster-growing groups. Nonaqueous hydrogen exchange was determined from tritium activity in the dried carcass. Less than 1% of the injected tritium exchanged with nonaqueous hydrogen during the equilibration period. Thus differences between TBWHTO and TBWdes in the younger animals could not be accounted for by nonaqueous hydrogen exchange but may have resulted from a larger loss of injected tritium, possibly in insensible water.
authors.affiliation: Department of Pediatrics, Baylor College of Medicine, Houston, Texas.
authors.forename: H P
authors.initials: HP
authors.lastname: Sheng
authors.forename: R A
authors.initials: RA
authors.lastname: Huggins
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism*; D001834:Body Water / Q000378:metabolism*; D001835:Body Weight; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium; D014867:Water
chemical_list: D014867:Water; D014316:Tritium