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SUMMARY
The gonadotrophic activities of crude glycoprotein fractions from pituitaries of man, sheep, chicken and carp and of partially purified follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the three tetrapod species were examined in both sexes of the lizard Anolis carolinensis. The piscine material did not show activity in the lizard but all mammalian and avian preparations promoted spermatogenesis, ovarian growth, ovulation and steroidogenesis. FSH preparations were far more potent than LH, in fact the actions of the LH preparations may have been due largely to FSH contamination. These findings are consistent with earlier conclusions that FSH alone may be able to stimulate all types of gonadal activity in lizards, except that high doses of FSH block ovulation. Comparisons of the relative potencies of the avian and mammalian preparations provide evidence for the zoological specificity of vertebrate gonadotrophins. In general, the relative potency of chicken gonadotrophins in lizards was greater than that estimated from standard rodent bioassays: i.e. the lizard is relatively more sensitive to chicken gonadotrophin than the rodent.
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ABSTRACT
A glycoprotein of neurohypophysial origin was found to have cofractionated with FSH prepared from pituitary glands of the green turtle, Chelonia mydas. Antiserum raised against this preparation contained high antibody titres and affinity for the neurohypophysial component and allowed development of a specific radioimmunoassay to monitor its purification and distribution in the brain. Immunocytochemistry revealed that the glycoprotein was concentrated in the pars nervosa and associated nerve tracts passing through the median eminence to the supraoptic and paraventricular nuclei; similar distributions were observed in turtles and rats. The antiserum to the turtle material bound radiolabelled rat vasopressin (VP)-neurophysin and precipitated precursors of this neurophysin, but it did not cross-react with rat oxytocin-neurophysin. An amino-terminal alanine was also consistent with the structure of rat VP-neurophysin, but the turtle molecule was larger than the corresponding rat molecule. Limited tryptic digests of the turtle glycoprotein contained two components, one of which bound to lysine VP.
Both components contained carbohydrate, but only the one which bound to VP cross-reacted in a radioimmunoassay for rat VP-neurophysin. The apparent surge in plasma immuno-FSH at the time of oviposition previously described in the turtle probably represented release of a neurophysin-like 'carrier' molecule associated with secretion of the neurohypophysial hormone (e.g. arginine vasotocin; AVT) responsible for oviduct contractility. These data suggest that the neurohypophysial glycoprotein represents a partially processed AVT precursor and provide the first biochemical evidence of a mammalian-like biosynthetic pathway for neurohypophysial hormones in a non-mammalian species.
J. Endocr. (1984) 103, 97–106