Reevaluation of the relative activities of the pituitary glycoprotein hormones (follicle-stimulating hormone, luteinizing hormone, and thyrotrophin) from the green sea turtle, Chelonia mydas.

The discovery that the follicle-stimulating hormone (FSH) previously prepared from the green sea turtle, Chelonia mydas, contained a major neurohypophysial contaminant prompted a repurification and characterization of the glycoprotein hormones in this turtle. Results reaffirmed the physicochemical distinctiveness of the three hormones. Minimal cross-contamination between hormones (less than 2%) was achieved by ion-exchange chromatography, subunit dissociation (of contaminating luteinizing hormone (LH], gel filtration, and immuno-affinity chromatography. New preparations of FSH and thyrotrophin (TSH) derived from adult pituitaries proved to be more potent than those described previously (the degree depending on the nature of the assay); FSH showed the expected increase in activity based on estimated contamination of previous preparations. LH was similar to original preparations except for enhanced activity in FSH radioreceptor assays. Binding assays (in heterologous and homologous systems) again demonstrated the general absence of an FSH-specific receptor in the reptilian (chelonian and squamate) testes. In an in vivo bioassay in the lizard Anolis, the turtle FSH was orders of magnitude more potent than LH in stimulating both testis growth and androgen secretion, but in vitro LH was considerably more potent than FSH in stimulating androgen secretion in squamate and chelonian testes. Thus, the possibility exists that androgen secretion in some chelonian systems may exhibit a high degree of LH specificity like that of mammals and birds.