Poster Title

Patterns of Energy Allocation in Immunochallenged and Testosterone-treated White-footed Mice (Peromyscus leucopus).

Institution

Murray State University

Abstract

The cost of mounting an immune response was studied in normal and testosteronetreated male white-footed mice (Peromyscus leucopus) that were fed ad libitum. We tested the null hypotheses: 1) there is no change in metabolic rate during an immunochallenge and 2) there is no change in energy allocation to other systems during an immunochallenge. We established four groups of animals: 1) control, 2) testosterone-treated, 3) immunochallenged, and 4) immunochallenged plus testosterone. Testosterone propionate injections were given to elevate the level of testosterone. Immunochallenged animals were injected with sheep red blood cells (SRBC) and phytohemagglutin (PHA) to challenge the humoral and cell mediated branches of the immune system, respectively. To test our first hypothesis we determined the daily metabolic rate (DMR) and resting metabolic rate (RMR) of each animal. To test our second hypothesis we measured the masses of the body organs. There was a significant increase in RMR in the immunochallenged animals, but no difference in DMR among groups. Thus, our first hypothesis was partially supported. Immunochallenge had no significant effect on the masses of intestinal and vital organs, but was associated with a significant increase in the masses of the reproductive organs. We, therefore, rejected our second hypothesis. Our findings indicated that there was a significant cost associated with mounting an immune response, as indicated by the increase in RMR. In addition, there was an increase in energy allocation to the reproductive organs. Thus, under good conditions there was no trade-off in energy use for immunity and reproduction.

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Patterns of Energy Allocation in Immunochallenged and Testosterone-treated White-footed Mice (Peromyscus leucopus).

The cost of mounting an immune response was studied in normal and testosteronetreated male white-footed mice (Peromyscus leucopus) that were fed ad libitum. We tested the null hypotheses: 1) there is no change in metabolic rate during an immunochallenge and 2) there is no change in energy allocation to other systems during an immunochallenge. We established four groups of animals: 1) control, 2) testosterone-treated, 3) immunochallenged, and 4) immunochallenged plus testosterone. Testosterone propionate injections were given to elevate the level of testosterone. Immunochallenged animals were injected with sheep red blood cells (SRBC) and phytohemagglutin (PHA) to challenge the humoral and cell mediated branches of the immune system, respectively. To test our first hypothesis we determined the daily metabolic rate (DMR) and resting metabolic rate (RMR) of each animal. To test our second hypothesis we measured the masses of the body organs. There was a significant increase in RMR in the immunochallenged animals, but no difference in DMR among groups. Thus, our first hypothesis was partially supported. Immunochallenge had no significant effect on the masses of intestinal and vital organs, but was associated with a significant increase in the masses of the reproductive organs. We, therefore, rejected our second hypothesis. Our findings indicated that there was a significant cost associated with mounting an immune response, as indicated by the increase in RMR. In addition, there was an increase in energy allocation to the reproductive organs. Thus, under good conditions there was no trade-off in energy use for immunity and reproduction.