A Chemocytological Investigation of the Avian Adrenal Medulla

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Abstract
The relative proportions of adrenaline (A) and noradrenaline (NA)-containing areas have been planimetrically estimated in 12 avian species representing several orders and families. There is great variability in percentages of A and NA-containing cells in the suprarenal medulla of these species. Three possibilities are suggested to explain this hormonal diversity. (1) methylation of medullary hormones is dependent on the cortico-medullary ratio; (2) relative abundance of A and Na in a species is determined by the degree of aggression and predation behavior manifested by it; and (3) differing association of A and NA in this class of vertebrates may be connected with avian phylogeny. The latter possibility appears to best fit the data. This assumes increased efficiency of hormonal methylation during the course of avian evolutionary ascent. This report also indicates that chromaffin tissue of birds is rich in acetal phosphatides, metachromatic substances and acid phosphatase. Two species (H. smyrnensis and A. phoenicurus), however, have no medullary metachromatic materials.

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