Regional differences in androgenic sensitivity of the chick comb and effects related to volume of inuncted vehicle

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Abstract
Combs of chicks were divided surgically into posterior (P‐comb) and anterior (A‐comb) portions of equal weight, thus providing two separate target organs in the same animal. Inunction with testosterone propionate stimulated equal increments in P‐ and A‐combs with regard to values for length + height, but weight of the P‐comb increased significantly more than that of the A‐comb as a result of greater increase in width of the P‐ than of the A‐comb. The P‐ was five times more responsive than the A‐comb and contained larger amounts of ground substance as shown by histological examination and larger amounts of hexosamine as shown by chemical study. It was concluded that these two portions of the comb differed greatly in capacity to grow in response to androgenic stimulation.Reduction in the volume of the vehicle from 5 to 0.5 μl resulted in a sevenfold greater response of the chick comb to androgens.Restriction in the volume of vehicle and the use of the P‐comb alone did not alter the precision of assay. Use of these procedures would permit measurement of androgens in amounts hitherto too small for assay.