On Chick Assay Method for Avian Gonadotropins*

One of the major problems in studies on gonadotropin(GTH)is to use the appropriate assay method. While numerous methods of bio-assay for GTH were used by many workers, one of those was based on the weight-increases of gonad and accessory sexual organ of assay animals, and this might be classified into following three groups according to the species of assay animals;rat, mouse and chick method. Greep et al.(1936)and Cartland and Nelson(1938)concluded that gonads and accessory organs of immature rats suited to assay end-point for GTH. The method in which immature mice were used as assay animal was established by Levin and Tyndale(1937). Breneman(1936, 1945a)indicated that small amounts of anterior pituitary principle would elicit the increase of testicular weight of chicks which were kept without food and water for a test period of 96 hrs. When the potency of GTH from the fowl anterior pituitary was assayed, the rat(Meyer et al. 1939), the mouse(Riley and Fraps, 1942a, b, )and the chick assay(Breneman, 1945b)were used. However, there are no previous reports on the comparison of sesitivities in three species of assay animal to avain GTH, although Evans et al. (1940)used the GTH preparations of mammalian origin as their administered hormone to assay animals for the comparison of sensitivities. Thus, it remains undetermined whether their results on mammalian GTH may be applicable to avain GTH or not. On the other hand, Byerly and Burrows(1938)used the chicks as assay animal when they assayed gonadotropic activity of chicken pituitary. Breneman(1945b), studying the application of mice and chicks to the assay of fowl pituitary GTH, suggested that the fact that same species of donor and assay animal was used may be a contributing factor in the excellence of the responses in the assay. Recently Nalbandov et al. (1951)and Das and Nalbandov(1955)claimed that an avian peculiar GTH(so called an avian third GTH)possessing different properties from mammalian GTH was contained within the avian pituitary and acted only to ayes effectively. The purpose of this study is to compare the results obtained from the assay of fowl pituitary GTH on the immature rat, the immature mouse and the one day-old chick, and afterwards to establish the quantitative assay of the chick method.