Erythropoietin assay in mice made polycythemic by transfusion of heterologous red cells

A simple in vivo bioassay suitable testing of quality control of recombinant human erythropoietin (rHu-EPO) analogues was developed. Mice made polycythemic by intraperitoneal injection of 1.2 ml of a 80 per cent suspension of heterologous (rat) red cells were used as assay animals and splenic 59 Fe uptke as expression of the response to rHu-EPO. The assay took three days and the following schedule is propose: 1)intraperitoneal injection of 1.2 ml of washed packed red cells obtained from donor rats, 2) subcutaneous injection of test material 4-5 h after transfusion, 3) intravenous administration of 59 Fe tracer 48 h later, and 4) determination of splenic isotope uptake 6 h after injection. This method for the in vivo biossay of rHu-EPO analogues is an economical and reliable alternative to the existing bioassays of the hormone

Unmodified erythropoietic response to a beta adrenergic agonist in hypothyroid mice

Los agonistas beta-adrenérgicos poseen la propriedad de estimular la eritropoyesis en el modelo del ratón policitémico mediante inducción de la secreción de eritropoyetina. Considerando la existencia de un cúmulo de evidencias que indica que las hormonas tiroideas y las catecolaminas están íntimamente relacionadas, el objetivo del presente trabajo fue estimar la potencia eritropoyética del isoproterenol, un agonista beta-adrenérgico bien conocido, en ratones hipotiroideos. Animales adultos de la cepa CF-1 fueron alimentados con dieta estandard para roedores y agua (eutiroideos) o solución al 0.1 por ciento de propiltiouracilo durante 37 dÝas. La concentración de T4 en plasma, medida por RIA, fue 1.75 mug/ml y < 1.0 mug/ml en ratones eutiroideos e hipotiroideos, respectivamente. Los animales fueron transfundidos con 1.0 ml de eritrocitos homólogos y el efecto eritropoyético de 50, 500 o 5000 pg/kg de isoproterenol estimado mediante el método de incorporación de (59)Fe al eritrón. No se observaron diferencias estadísticamente significativas (P<0.05, test de t no apareado) entre animales eutiroideos e hipotiroideos. El hipotiroidismo, por lo tanto, no afecta la secreción de eritropoyetina inducida por isoproterenol en las presentes condiciones experimentales.

Immunoreactive erythropoietin in rodent submaxillary gland. Autonomic control of exocrine secretion and factors influencing its concentration

The SMG of mice and rats contain a heterologous group of biologically active factors. Some are well known, can be obtained at high purity and are well-characterized. There is strong evidence for the presence of others although they have not been purified. Finally, some of them are questionable and/or have not yet been characterized. EPO would be one of the factors whose presence in the SMG is strongly suspected, although its biological activity has not been demonstrated yet. Its presence in the gland, therefore, is only supported by radioimmunoassay data and immunocytochemical methods. Immunoreactive EPO is undetectable in the mouse SMG until the 30th day of postnatal life, increasing thereafter at a uniform rate and reaching adult levels by 50-60 days of age. The parallelism between its concentration in extracts of the gland, the size and relative proportion of GCT cells, could be accepted as indirect evidence for its localization in these cells. The rise in iEPO concentration in SMGs after androgen treatment, its fall following orchiectomy, and its reduction after duct ligation in proportion to the degree of degranulation of GCT cells lend support to the above hypothesis. Salivary secretions induced by either NE or ISO contain high levels of iEPO. A significant depletion of gland content is also observed. These two sets of data indicate that SMG exocrine iEPO secretion occurs and that this secretion is mediated by adrenergic receptors. The question whether the SMG also functions as an endocrine organ in relation to EPO can not be answered at present.