Abstract
AbstractA study was made of the concentration and cellular localization of serotonin in the thyroid gland of the dog. This species is characterized by a low level of serotonin in the adult thyroid gland. Endogenous serotonin consequently cannot be demonstrated by fluorescence microscopy following treatment of frozen‐dried adult thyroid tissue with formaldehyde vapor. In contrast, the thyroid concentration of serotonin was found to be high, in both beagle and basenji (purebred dogs of European or African origin respectively), around the time of birth. The serotonin concentration then fell rapidly as development of the animals proceeded. This pattern also seemed true of the rabbit. When the concentration of serotonin was high, just prior to birth, a yellow fluorophore, probably the condensation product formed between serotonin and formaldehyde could, as in other species, be demonstrated in parafollicular cells after exposure of tissue to formaldehyde gas. Thyroid follicular cells never showed serotonin but instead, a striking accumulation of autofluorescent apical dense bodies (0.3–1.0 μ in diameter), probably lysosomes, occurred during the first year of life.
Published Version
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