Prolactin bioassay and hyperprolactinemia.

The Nb2 rat lymphoma bioassay (BA) for prolactin (PRL) was performed in 26 subjects with hyperprolactinemia, 17 of whom had radiologic evidence of a pituitary adenoma. All subjects were treated with the long acting dopamine agonist CV 205-502. The radioimmunoassay (RIA) PRL significantly decreased with treatment but the BA/RIA PRL remained essentially the same, indicating that the relative bioactivity was unaffected.

Prolactin bioassay in schizophrenia before and after neuroleptics.

Fifteen drug-free schizophrenic male inpatients and 14 normal control subjects were studied. The schizophrenic subjects had a significantly lower ratio of bioassay prolactin to radioimmunoassay prolactin before neuroleptic treatment than they did after treatment. The ratio was lower in the drug-free patients as compared with normal controls. These findings suggest that neuroleptic medications may alter the molecular forms of serum prolactin. The results also suggest that drug-free schizophrenic patients may have a different pattern of prolactin variants than normal subjects and that this difference could be secondary to a disordered tuberoinfundibular dopamine system or long-term effects of neuroleptic drugs.

Chondrocyte growth factor from the human pituitary gland.

Extracts of frozen human pituitaries were mitogenic in a fetal rabbit chondrocyte bioassay. In the presence of 10% fetal bovine serum, a 10-fold increase in chondrocyte cell number was observed upon addition of the pituitary factor to the culture medium. After gel filtration, the chondrocyte growth factor eluted with proteins of approximately 40,000 molecular weight. These fractions were pooled and purified further upon ion exchange chromatography using DEAE-cellulose. The most active fraction stimulated cell proliferation in a dose-dependent manner down to 10 ng/ml. The chondrocyte growth factor was trypsin- and heat-sensitive (100 degrees C, 10-15 min). Its isoelectric point (pI 7.9) was different from bovine brain and pituitary fibroblast growth factor (pI 4.8-5.8 and pI 9.5, respectively. Unlike the somatomedins and epidermal growth factor, it was acid-labile. Preparations of human growth hormone, prolactin, luteinizing hormone, and follicle-stimulating hormone, prolactin, luteinizing hormone, and follicle-stimulating hormone, as well as vasopressin and oxytocin, were inactive in the bioassay, demonstrating that the human pituitary contains a chondrocyte growth factor which appears to be distinct from these anterior and posterior pituitary hormones.

Radioimmunoassay for human growth hormone using monoclonal antibodies.

Radioimmunoassay (RIA's) for human growth hormone (hGH) employing monoclonal antibodies (Mab) were compared with a conventional clinical RIA using polyclonal antibodies (PAb). Several MAb displayed sensitivities (defined as the concentration of hormone required for 50% inhibition of binding of 125I-hGH) for hGH in the RIA which were equivalent to those of PAb. Those MAb with the greatest sensitivity for hGH displayed an equal affinity for human placental lactogen (hPL), whereas those with lower sensitivity for hGH, cross-reacted minimally with hPL. The concentrations of hGH in human serum samples were determined with MAb and the values showed a high degree of correlation with those obtained by PAb. It is therefore concluded that MAb are useful for the development of clinical RIA's for polypeptide hormones.

Inter-batch quality differences in purified human prolactin.

During the past four years, we secured six batches of purified human prolactin for iodination by the same lactoperoxidase technique. Two of these batches gave us more satisfactory results in terms of assay sensitivity and consistency than did the others, regardless of the antiserum used. Gel filtration of 125I-labeled hormone revealed that these two batches were composed of at least 55% "small" prolactin while the other four batches contained from 20 to 68% "big" prolactin. This qualitative difference was the most important contribution to assay discrepancies.