Effect of food or water restriction on erythropoiesis in mice: relevance to "anemia" of space flight.

Dehydrated mice showed a negative energy balance and hemoconcentration similar to that thought to occur in men during space flight, although the mechanism producing these changes may be completely different. The relative importance of dehydration and a negative energy balance in producing erythroid suppression has been investigated. The initial suppression appeared to be due to a reduced food intake. Thereafter, this negative energy balance produced about 40% of the erythroid suppression, the severity of which was augmented by dehydration. The decreased food consumption appeared to suppress erythropoiesis by reducing the sensitivity of the target cells in the spleen to erythropoietin (Ep), the erythropoietic hormone. Hemoconcentration decreased titers of Ep thus also suppressing erythropoiesis. Attempts to alleviate the effects of water deprivation and reduced food consumption by effects of water deprivation and reduced food consumption by water injections and the feeding of supplemented diets were only marginally effective at ameliorating the erythroid suppression. These studies indicate the importance of maintaining an adequate energy and fluid balance in the regulation of erythropoiesis.