SIMULTANEOUS BIOASSAY OF EXOPHTHALMOS-PRODUCING AND THYROTROPHIC SUBSTANCES

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Abstract
Further research on EPS and its relationship to TSH [thyro-tropin] demands improved methods of assay. An EPS bioassay, based on a teleost fish, Carassius carassius L., and the valid measuring of the volume changes in the orbital tissues by extended exophthalmometry, has been developed and evaluated. It was found that the variance of response was strongly influenced by the technique of injection, the duration of assay, and the measuring method. Linear log dose-response regressions were obtained with single injections in the interval of 50 to 5000 [mu]g of an anterior pituitary hormone preparation (Ambinon, Organon). The mean index of precision equalled 0.27 for the most favorable technique. The median threshold dose was 21 [mu]g. The assay was completed in 3 hr. Hypophysectomized fishes were less responsive than normal fishes. Thyroxine treatment resulted in increased proptosis and impaired precision of EPS assay. Two strains of the same species were studied. It is suggested that the observed differences in assay performance is related to the magnitude of endogenous thyroxine output. Radiation inactivation of bovine EPS disclosed a radiosensitive molecular weight of 4.7 x 104.