INTERACTING EFFECTS OF THYROID ACTIVITY AND DIETARY LEVEL OF VITAMIN A ON ERYTHROCYTE FRAGILITY IN THE CHICKEN

Abstract

The level of dietary vitamin A is shown to affect the osmotic stability of chick erythrocytes in hypotonic solutions. In chicks fed an excess of vitamin A, induced hyperthyroidism shifts the osmotic fragility curves, which indicates that an increase in the proportion of more stable cells has occurred. When the level of dietary vitamin A is normal, induced hyperthyroidism does not appreciably alter the osmotic fragility curve. It is concluded that the increased fragility of erythrocytes from chicks fed an excess of vitamin A may be an indirect effect of suppression of thyroid activity with a consequent increase in the proportion of older, more fragile cells in the blood.