Binding of thyroid hormone to isolated ovarian nuclei from a freshwater perch, Anabas testudineus

High affinity, low capacity 3,5,3'-triiodo-L-thyronine (T3) specific binding was detected in the pure nuclei preparation from ovarian tissue of freshwater perch by employing an in vitro thyroid hormone binding assay. Under standardized assay conditions of pH 7.0 at 30 degrees and 1 hr incubation time, the binding in the ovarian nuclei was saturable with a Kd 9.1 X 10(-9) M. For comparison, a Scatchard analysis of T3 binding to perch hepatic nuclei was done and a higher Kd value (16.89 X 10(-9) M) with twofold increase in maximum binding capacity (MBC 8.882 and 4.312 pmol/mg DNA in liver and ovary, respectively) was observed. Competitive inhibition studies showed ovarian T3 binding to be hormone specific with relative binding affinities comparable to T3 binding in other systems. T3 binding to the nuclear preparation from tail kidney and brain tissue of perch was considerably lower in comparison to liver and ovarian nuclei. Functional relevance of T3 binding to perch ovarian nuclei was tested by incubating ovarian tissue in vitro with T3. T3 significantly (P less than 0.001) increased protein synthesis in comparison to control.