Involvement of prolactin in the regulation of plasma calcium levels in the newt, Cynops pyrrhogaster.

In the newt, Cynops pyrrhogaster, parathyroidectomy (PTX) brought about a marked decrease in the concentration of plasma calcium. The animals recovered from the hypocalcemia by 15 days after the operation if the pituitary gland was left intact. After PTX, no significant changes in the plasma sodium concentration were observed. Experiments were then conducted to obtain direct evidence that endogenous prolactin (PRL) is involved in this recovery process. Recovery of the calcium level after PTX was blocked by administration of an antiserum raised against newt PRL. In newts deprived of both the pituitary and parathyroid glands, no recovery from hypocalcemia was observed. Administration of newt or ovine PRL to parathyroidectomized-hypophysectomized newts significantly elevated the blood calcium level. After PTX, the concentration of immunoassayable PRL in the blood rose to 10 times the value in sham-operated animals. These results indicate the involvement of PRL in calcium homeostasis in newts with a shortage of parathormone.