Developmental regulation of growth hormone binding in the gilthead sea bream, Sparus aurata.

The occurrence of growth hormone (GH) binding was investigated in the gilthead sea bream larva, Sparus aurata, using recombinant trout GHII (rtGH) as a tracer. GH binding was detected in all the specimens examined (5, 17, 27 and 40 days after hatching). At 40 days after hatching, we observed a concentration of GH binding in the head region. Specific binding was dependent on protein membrane concentration and Scatchard plots showed a single class of high affinity and low capacity binding sites. Specific binding was inhibited by rtGH and ovine GH in a dose dependent manner. Chinook salmon prolactin and chinook salmon gonadotropin did not compete for 125I-rtGH binding sites. To our knowledge, this is the first report that indicates the presence of specific and saturable GH binding sites during early growth and development of a fish species.