Elevation of plasma prolactin concentrations by low temperature is the cause of spermatogonial cell death in the newt, Cynops pyrrhogaster.

Temperature plays an important role in reproduction of urodeles. Spermatogenesis in newts is arrested when the environmental temperature lowers. We found that transfer of newts, Cynops pyrrhogaster, to low temperature (8 and 12 degrees C) caused cell death of spermatogonia just before meiosis and elevation of prolactin concentration in the newt plasma. Injection of a dopamine antagonist (pimozide), which is known to increase the plasma prolactin concentration, to the newt caused significant increase of spermatogonial degeneration, whereas treatment with an agonist (bromocryptin), which is known to decrease the prolactin concentration, suppressed the cell death. Finally, injection of anti-prolactin serum into the newts which had been transferred to low temperature almost completely inhibited the spermatogonial degeneration for as long as 3 days. These results demonstrate that low temperature caused elevation of prolactin concentration in the newt blood, which induced cell death of spermatogonia just before meiosis.