Plasma prolactin (PRL) and vitellogenin (VTG) concentrations were determined during the annual reproductive cycle of the newt Triturus carnifex Laur. Plasma PRL was measured by a radioimmunoassay using purified newt (Cynops pyrrogaster) PRL as standard and radioligand and its antibodies. Using ELISA, plasma VTG titers were related to ovarian weight. The trends in PRL differed in the two sexes: the PRL changes seemed to be related with vitilellogenic processes in the female, whereas they were more related to reproductive behavior in the male.
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