The effect of clenbuterol on basal protein turnover and endogenous nitrogen loss of sheep

J E INKSTER, Francis Dickon Deberdt Hovell, D J KYLE, David Stanley Brown, Gerald Lobley

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Abstract

Seven measurements of the effect of clenbuterol on basal nitrogen excretion (UN,), and protein turnover were made in six female sheep. The sheep were sustained by the intraruminal infusion of energy as volatile fatty acids to provide maintenance, but given no protein (N-free) for 12 d (6 d control, 6 d
clenbuterol). Clenbuterol reduced UN, by 20%, but only on day 2 of the 6 d subperiod. Protein flux (equivalent to degradation on N-free nutrition), measured on day 6 by the irreversible loss of leucine was significantly increased (12 %) by clenbuterol. Amino-N oxidation measured by N excretion was unchanged and, therefore, protein synthesis was also increased. During the 12 d N-free period, the recovery of urinary total N (Kjeldahl) as the sum of urea, ammonia, creatinine and purine derivatives, declined from 87.7 to 74.2 %. The form of this missing N was not identified. The effect of clenbuterol of increasing both degradation and synthesis is unlike that reported in the literature for animals receiving protein when, in general, synthesis is unchanged and degradation reduced. This could be due to a different effect of clenbuterol in the N-free state, or to unchanged effects on protein pools other than muscle whose relative contribution to protein metabolism is different in the N-free state.
Original languageEnglish
Pages (from-to)285-296
Number of pages12
JournalBritish Journal of Nutrition
Volume62
Issue number2
Publication statusPublished - Sep 1989

Keywords

  • Clenbuterol
  • Protein turnover
  • Nitrogen loss
  • Sheep

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