The goal of this work was to initiate a systematic investigation of the possible substrates for muscle glyconeogenesis under physiological circumstances--during recovery from prolonged submaximal exercise. The hypothesis was that amino acids mobilized from possibly increased body protein breakdown (in particular muscle protein degradation), or glycerol liberated from catabolism of body fat (especially intramuscular fat) during and after exercise might serve as substrates for muscle glyconeogenesis after exercise. In order to assess whole body protein breakdown, muscle myofibrillar protein degradation during and after exercise as well as to determine the incorporation of putative substrates into muscle glycogen during postexercise recovery, twelve-hour-fasted rats were infused intravenously with: (a) $\sp $C-U-urea, (b) $\sp $C-U-threonine (a representative of gluconeogenic amino acids) and $\sp3$H-6-glucose, and (c) $\sp $C-U-glycerol and $\sp3$H-6-glucose throughout two-hour basal, four-hour swim (or rest) and three-hour postexercise recovery periods. Arterial blood samples were taken every hour. Soleus, white and red gastrocnemius muscles were excised and assessed for 3-methylhistidine (3-MH) and tyrosine contents as well as for total and radiolabelled glycogen contents at the end of the postexercise recovery. The results indicate that: (1) whole body protein breakdown and muscle myofibrillar protein degradation increase significantly during and after prolonged swimming in white and red gastrocnemii as evidenced by an increased rate of urea production and increased 3-MH level in blood and in these muscles, respectively; (2) glyconeogenic amino acids released from increased body proteolysis appear to serve as substrates for glyconeogenesis after exercise in at least red gastrocnemius muscle, as demonstrated by the fact that nearly 11% of the label arising from $\sp $C-U-threonine and incorporated into muscle glycogen could be accounted for by muscle glyconeogenesis; and (3) circulating glycerol does not play a role in muscle glyconeogenesis. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/10224 |
| Date | January 1994 |
| Creators | Wang, Qian. |
| Contributors | Radziuk, Jerry, |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 163 p. |
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