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

Body weight loss during acute hypoxia: effects of increased convective oxygen transport or previous acclimation

La pérdida de peso corporal y el retardo del crecimiento corporal que se observan en ratas expuestas a condiciones de altura simulada podrían estar relacionados con la reducción del transporte convectivo de O2 (COT) inducida por hipoxemia. El presente estudio fue realizado para determinar si la policitemia transfusional, el incremento de la afinidad de la hemoglobina por el O2, o la aclimatación previa a hipobaria (factores que incrementan (COT) son capaces de contrarrestar los efectos señalados sobre el peso corporal durante el "período inicial" de la exposición, el que puede se considerado como um parámetro útil para comprobar la efectividad de la aclimatación. La policitemia fue inducida en ratas jóvenes mediante dos inyecciones ip de 2,5 ml/100g de suspensión de eritrócitos homólogos al 80 por ciento. La disminución de la P50 fue inducida en ratas adultas mediante la administración de o.5g/dl de cianato de sodio en el agua de bebida durante 3 semanas. Ambos tratamientos indujeron una menor pérdida de peso lo que sugeriría que la compensación fue probablemente insuficiente. Cuando ratas jóvenes fueron aclimatadas a condiciones de altura simulada, se observó un marcado incremento del peso corporal cuando perdieron peso en la misma proporción que la observada en animales controles no aclimatados previamente. Los resultados obtenidos indican que el incremento del COT no previene los efectos estudiados de la exposición a hipobária y sugieren que la hipofagia y la pérdida inicial de peso, así como la depressión secundaria del crecimiento corporal, podrían ser consideradas como un mecanismo protector contra la hipoxia resultante

Additive effects of dietary protein and energy deficiencies on mandibular growth in the weanling rat

Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.

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.