Effect of Arginine Deficiency on Growth and Intermediary Metabolism in Rats

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Abstract
Male, Sprague-Dawley rats (35–40 g) were fed a purified diet containing L-amino acids with and without arginine. Feed intake for the 30 rats fed no arginine was lower than that of 30 control rats throughout the 18-day feeding period (P < 0.05). Average daily weight gains were lower for the deficient group after 2 days (P < 0.01). All animals were in positive nitrogen balance with control rats showing higher retention (P < 0.01). Weanling rats showed marked increases in urinary citrate, isocitrate, malate, cis-aconitate, and orotate after 48 hours of consuming the deficient diet. After 18 days of feeding the deficient diet, urinary citrate, isocitrate, cis-aconitate, and orotate remained highly elevated compared with control levels. During the first 24 hours of consuming the arginine-deficient diet, the total urinary orotate was 65 times higher than control levels for mature rats, and by the end of day 3, their 24-hours orotate excretion was 175 times higher than control levels. Urinary urea excretion increased dramatically during the first 24 hours of consuming the deficient diet and with the duration of feeding. Paired-feeding showed that the increase in urinary urea, citrate, or orotate was not due to depressed feed intake. The data indicate that during arginine deficiency, the urea cycle is limited in its capacity for urea synthesis and consequently, there is a rise in urinary excretion of citrate and orotate. The evidence indicates that immature and mature rats have limited reserves of arginine from endogenous synthesis.

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