Plasma ascorbic acid concentrations in a population of rhesus monkeys (Macaca mulatta)

Although monkeys frequently are used as animal models for ascorbic acid studies whose results are extrapolated to humans, little information is available on the normal levels of this vitamin in large populations of animals classified by sex, age, or physiologic state such as pregnancy or lactation. The purpose of this report is to provide these values and compare them to the same parameters in humans, pointing out similar and dissimilar trends. Plasma samples were obtained from a troop of 167 rhesus monkeys (Macaca mulatta) and analyzed for ascorbic acid by using the 2,4-dinitrophenyl hydrazine method. Results obtained for ascorbic acid concentrations in plasma showed no differences between sexes. A significant (P< 0.0001) lowering effect was observed in aging versus young animals. Pregnant and nonpregnant females had similar ascorbate values, and lactating monkeys had slightly elevated levels. We conclude that rhesus monkeys and humans exhibit some of the same characteristics of ascorbic acid metabolism, such as an age-related decrease in ascorbate and the maintenance of these levels during lactation. However, a difference between species was noted with gender. Women maintain higher ascorbate concentrations than do men, whereas no differences in concentrations of this vitamin were observed between female and male monkeys.