Secretion of dopamine into hypophysial portal blood by rats bearing prolactin-secreting tumors or ectopic pituitary glands.

Abstract

Catecholamines were quantified in hypophysial portal plasma obtained from cycling diestrous rats and from noncycling diestrous rats with hyperprolactinemia due to PRLsecreting pituitary explants or a PRL-secreting pituitary tumor. In rats bearing PRL-secreting tumors, the plasma concentration of PRL was 4450 ± 938 ng/ml (mean ± SE), whereas in cycling diestrous animals the plasma level of PRL was 16 ± 2.2 ng/ml. The concentration of dopamine in hypophysial portal plasma of tumor-bearing rats (2.0 ± 0.3 ng/ml) was significantly greater (P < 0.05) than that in diestrous rats (1.1 ± 0.2 ng/ml). The anterior pituitary content of PRL was 18 ± 1.5 μg in cycling diestrous animals and 9 ± 0.8 μg in tumor-bearing rats. The adrenals from tumor-bearing animals were much heavier (155 ± 14 mg) than those from cycling diestrous rats (58 ± 1.2 mg). The concentration of dopamine in portal plasma from tumor-bearing adrenalectomized rats was 2.0 ± 0.5 ng/ml, similar to that in portal plasma from tumor-bearing intact animal...