Abstract
Cycloleucine, chemically known as 1-aminocyclopentane-1-carboxylic acid (ACPC) is not a naturally occurring amino acid (see Figure 1). Metabolic studies of ACPC in mice and rats have shown that it is not metabolized nor excreted rapidly; therefore, blood and peripheral tissue levels are maintained for several days (1, 2). Ross et al (3) reported a decreased growth rate in animals fed a diet containing ACPC and suggested it may function as an amino acid antagonist. Clark et al (4) proposed that its effect on growth rate and amino acid pools were secondary to a depressed food intake.
The results obtained in the present study suggest yet another mechanism of action of ACPC on reducing food efficiency in rats fed a purified high starch diet.
Materials and methods. Male Wistar rats (160–170 g) were given a standard laboratory Purina Chow or high carbohydrate diet 2 in powdered form ad libitum to facilitate estimation of daily food consumption. They were housed individually in open wire bottom cages. Water was available at all times. In experiment I, 5 days after commencement of the high carbohydrate diet, groups of animals received either the basal ration or ACPC incorporated into the diet at the following levels: 0.0125, 0.025, 0.05, or 0.1%. In experiment II, ACPC and its chemically related amino acids (l-(–)-proline, l-4-hydroxyproline, glycine, l-leucine, or l-isoleucine) were admixed separately to the Purina Chow diet at 0.5 mg/g diet (0.05%) or 1 mg/g diet (0.1%), respectively. Animals were given ad libitum for a period of 3 days.
Body weight and food consumption were monitored throughout experimental period. Blood was obtained by cardiac puncture and portions of the pancreas, small intestine, and liver were collected and chilled rapidly from anesthetized rats at the end of the studies.
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