Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Food and Nutrition


Defective protein metabolism in association with subnormal lean body mass has been proposed as an underlying factor in the obesity of the Zucker rat. In contrast to the obese male Zucker rat, obese female rats maintain normal or above normal lean body weight despite the obesity;In Experiment 1, female Zucker rats were treadmill exercised from 12 to 17 weeks of age. Exercise decreased percent carcass fat and increased lean carcass weight of lean rats but not of obese rats. Although exercise did not affect 3-methylhistidine (3-MH) excretion in either genotype, obese rates excreted more 3-MH than lean rats did;In Experiment 2, female Zucker rats were fed ethynyl estriadiol (EE) from 10 to 18 weeks of age. Obese rats were more sensitive to EE feeding than lean rats were. EE feeding decreased lean carcass weight more markedly in obese than in lean rats. EE feeding in obese rats resulted in decreased heart, liver and spleen weights; whereas, in lean rats, heart and liver, but not spleen, weights were decreased by EE feeding. EE feeding had no effect on 3-MH excretion in either genotype;In Experiment 3, 25-day-old and 10-week-old female Zucker rats were injected with ('3)H-phenylalanine and incorporation of label into muscle and liver protein was measured. Obese 25-day-old rats incorporated less label into both muscle and liver protein than lean rats did. However, obese rats excreted less 3-MH than lean rats did. At 10 weeks of age, incorporation of label into liver and muscle protein and excretion of 3-MH were similar for lean and obese rats;These results support the hypothesis that defective protein metabolism is an underlying factor in the obesity of the female Zucker rat even though lean body mass is normal.



Digital Repository @ Iowa State University,

Copyright Owner

Catherine A. VandeVoort



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114 pages