Influence of recombinant chicken prolactin on thyroid hormone metabolism in the chick embryo.
The influence of a recombinant chicken prolactin (rcPRL) preparation on thyroid function was studied in 18- and 19-day-old chicken embryos. Displacement studies on hepatic microsomes indicate that this preparation does not compete with radiolabeled chicken growth hormone (cGH) for hepatic GH-receptor binding. In a first series of experiments rcPRL or immunoaffinity-purified cGH was injected intravenously in 19-day-old chicken embryos. After 2 hr, cGH increased plasma T3 in a dose-dependent way by inhibiting hepatic inner ring type III deiodination (IRD-III) and consequently T3 degradation. Outer ring deiodination (ORD-I) was not influenced confirming previous results. The rcPRL preparation (2 and 10 microg) did not influence plasma T3, but depressed T4 and raised hepatic IRD-III activity simultaneously, whereas no influence on hepatic ORD-I activity could be found. In a second experiment on 18-day-old embryos, it could be demonstrated that the effect of 2.5 microg cGH on plasma T3 and liver IRD-III lasted up to 6 hr after injection, whereas 2.5 microg cPRL affected plasma T4 and liver IRD-III up to 2 hr. Both rcPRL and cGH depressed rT3 up to 6 hr, whereas an injection of rcPRL, but not of cGH, elevated plasma concentrations of corticosterone. These results indicate that prolactin may have a role, together with GH, in controlling peripheral thyroid hormone metabolism.
Kühn
E R
ER
Laboratory of Comparative Endocrinology, Catholic University of Leuven, B-3000 Leuven, Belgium.
Shimada
K
K
Ohkubo
T
T
Vleurick
L M
LM
Berghman
L R
LR
Darras
V M
VM
D000818:Animals; D002642:Chick Embryo / Q000378:metabolism*; D002645:Chickens; D003345:Corticosterone / Q000097:blood / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology; D007453:Iodide Peroxidase / Q000187:drug effects / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D011388:Prolactin / Q000494:pharmacology*; D011869:Radioligand Assay; D011994:Recombinant Proteins / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects* / Q000378:metabolism; D013974:Thyroxine / Q000097:blood / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D014284:Triiodothyronine / Q000097:blood / Q000187:drug effects / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011994:Recombinant Proteins; D014284:Triiodothyronine; D011388:Prolactin; D013006:Growth Hormone; D007453:Iodide Peroxidase; D013974:Thyroxine; D003345:Corticosterone