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Biology of Reproduction, Vol 13, 371-380, Copyright © 1975 by Society for the Study of Reproduction

Steroid-Protein Interactions in Nonmammalian Vertebrates. II. Steroids Binding Proteins in the Serum of Amphibians; a Physiological Approach

B. MARTIN 1, and R. OZON 1

1 Laboratoire de Physiologie de la Reproduction Universite Pierre et Marie Curie, 12, rue Cuvier PARIS 75005 France


Steroid-protein interactions were studied in various urodelan and anuran amphibians: Pleurodeles waltlii, Salamandra salamandra, Ambystoma mexicanum, Rana temporaria and Discoglossus pictus. The detection of specific steroids binding serum proteins was determined by equilibrium dialysis and sucrose gradient centrifugation experiments. Binding constants were determined by using an equilibrium dialysis-scatchard plot method.

Amphibians possess proteins with high steroid affinity and limited capacity. These proteins may be classified in two groups according to their specificity:

a) the proteins binding specifically C21 steroids or "Amphibian corticosteroid binding protein" (A.CBP). The binding constants of corticosterone were determined in four amphibian species; in Rana temporaria serum, the association constant (Ka) at 4 C was 8.2 x 108 M-1, and the binding capacity was 1.3 x 10-7M.

b) the proteins binding specifically C18 and C19 sex steroids or "Amphibian sex steroid binding protein" (A.SBP). These proteins were found in all amphibian species studied. In Rana temporaria serum, Ka values for estradiol-17beta and testosterone were respectively 5.1 x 108 M-1 and 1.3 x 109 M-1 and the binding capacity 3.3 x 10-7M.

The correlation between the binding activities of specific steroids binding serum proteins and the endocrine activity from animals of both sexes, and from castrated, pregnant and sex-reversed animals, was examined. In a further analysis the effects of the administration of estradiol-17beta to the castrated female Pleurodeles and the effects of administration of thyroxine to the female Ambystoma mexicanum were observed.

 Submitted on June 2, 1974
Accepted on June 9, 1975






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Copyright © 1975 by the Society for the Study of Reproduction.