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A Comparison of sex steroid binding protein (SBP) in four species of teleost fish

journal contribution
posted on 2023-05-16, 12:53 authored by Hobby, AC, Pankhurst, NW, Dominic GeraghtyDominic Geraghty
A sex steroid binding protein (SBP) binding E2 with high affinity has been detected in a pleuronectid (greenback flounder Rhombosolea tapirina), two sparids (black bream Acanthopagrus butceri and snapper Pagrus auratus), and its presence has been confirmed in a salmonid (rainbow trout Oncorhynchus mykiss). SBP binding characteristics were measured using a hot saturation assay for trout, bream and snapper, and a cold saturation assay for flounder. Bound and unbound steroid were separated by incubation with dextran-coated charcoal (DCC). Affinity for E2 was highest in trout (kD = 0.44 nM), followed by bream (kD = 3.39 nM) and snapper (kD = 10.7 nM). The lowest affinity was found in flounder (kD = 84.7 nM). Binding capacity, however, was greatest in flounder (Bmax = 164 nM), followed by trout (Bmax = 92 nM), and then bream and snapper (Bmax = 50 and 39 nM, respectively). Binding of E2 to SBP had a very rapid rate of association, and most dissociation occurred within 5 min. To confirm that the plasma protein measured here was SBP, the relative binding affinities of SBP for a range of steroids were measured. In trout, bream and snapper, SBP bound E2 with the highest affinity, followed by T. In contrast, the relative affinity of T for flounder SBP was more than twice that of E2. The rank orders of affinity of binding indicate the importance of an unhindered 17β-hydroxyl group, and a 3-hydroxyl or 3-ketone group for high affinity binding to SBP. These requirements for high affinity binding are present in most animals possessing SBP and indicate conservation of the SBP molecule through evolution.

History

Publication title

Fish Physiology and Biochemistry

Volume

23

Pagination

245-256

ISSN

0920-1742

Department/School

Institute for Marine and Antarctic Studies

Publisher

Kluwer Academic Publishers

Place of publication

Netherlands

Repository Status

  • Restricted

Socio-economic Objectives

Fisheries - aquaculture not elsewhere classified

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