Tissue-specific regulation of potassium homeostasis by high doses of cationic amino acids.

The administration of l-arginine hydrochloride has been used for testing pituitary secretion in humans, and as an experimental model for induction of acute pancreatitis in rats and mice. Whereas in the first case, the administration of the amino acid is associated with hiperkalemia, in the model of acute pancreatitis no data are available on possible changes in potassium homeostasis. The present study shows that the acute administration to mice of l-arginine hydrochloride or other cationic amino acids almost duplicate plasma potassium levels. This effect was associated to a marked decrease of tissue potassium in both pancreas and liver. No changes were found in other tissues. These changes cannot be ascribed to the large load of chloride ions, since similar effects were produced when l-ornithine aspartate was administered. The changes in potassium levels were dependent on the dose. The displacement of intracellular potassium from the liver and pancreas to the extracellular compartment appears to be dependent on the entry of the cationic amino acid, since the administration of an equivalent dose of alfa-difluoromethyl ornithine HCl (DFMO), a non physiological analog of l-ornithine, which is poorly taken by the tissues in comparison with the physiological cationic amino acids, did not produce any change in potassium levels in pancreas and liver. The analyses of the expression of cationic amino acid transporters (CAT) suggest that the CAT-2 transporter may be implicated in the potassium/cationic amino acid interchange in liver and pancreas. The possible physiological or pathological relevance of these findings is discussed.

Off-label prescription of drugs at hospital.

OBJECTIVES: To develop a procedure for management of off-label medications, and to analyze the treatments, indications, and hospital units which will request them more frequently, as well as which variables will have an impact on the authorization decision, and its economic impact. METHODS: A procedure was designed where clinicians would complete request forms and the Hospital Unit would prepare reports assessing their efficacy, safety, convenience, and cost. The request forms for the past five years were analyzed. RESULTS: A total of 834 applications were received, and 88.1% of these were accepted. The authorization rates were higher for Paediatric Units (95.7% vs. 86.6%; p<0.05). The reasons for considering prescriptions as off-label were: different indication (73.2%), different combination (10.2%), different line of treatment (8.6%) and different age (8%). A 73.4% of requests were for antineoplastic drugs, and the most frequently prescribed were rituximab (120) and bevacizumab (103). The quality of evidence supporting the prescriptions was moderate-low, though no direct relationship with the likelihood of approval was demonstrated (p = 0.413). The cost of the approved medications was 8,567,537 €, and the theoretical savings for those drugs rejected was of 2,268,642 €. There was a statistically significant decrease in the authorization rate (p < 0.05, Student's t test) when spending increased. CONCLUSIONS: The responsibility for assessing off-label prescriptions has fallen on the Pharmacy Unit. It has not been demonstrated that the quality of evidence represents a decisive variable for approval of treatment; on the other hand, age and cost have demonstrated a significant impact.

Objetivos: Desarrollar un proceso de gestión de medicamentos en condiciones fuera de ficha técnica y analizar los tratamientos, indicaciones y unidades clínicas que los solicitan, qué variables influyen en la decisión de autorización y su impacto económico. Métodos: Se diseñó un procedimiento según el cual los clínicos cumplimentarían las solicitudes, el Servicio de Farmacia redactaría los informes valorando su eficacia, seguridad, conveniencia y coste, y la dirección médica tomaría la decisión de aceptar o no su uso. Se analizaron las solicitudes de los últimos cinco años. Resultados: Se recibieron 834 solicitudes, autorizándose el 88,1%. Las tasas de autorización fueron mayores para los Servicios Pediátricos (95,7% frente a 86,6%; p < 0,05). Las razones por las que las prescripciones se consideraron fuera de ficha técnica fueron: diferente indicación (73,2%), combinación diferente (10,2%), línea diferente (8,6%) y edad diferente (8%). El 73,4% de las solicitudes fueron de antineoplásicos, siendo rituximab (120) y bevacizumab (103) los más prescritos. La calidad de la evidencia que avalaba las prescripciones fue moderada-baja, aunque sin demostrar relación directa con la probabilidad de aprobación (p = 0,413). El coste de los medicamentos aprobados fue de 8.567.537 € y el ahorro teórico de los denegados 2.268.642 €. El porcentaje de autorización disminuyó según aumentó el gasto de manera estadísticamente significativa (p < 0,05, test t de Student). Conclusiones: La responsabilidad de evaluación de las prescripciones fuera de ficha técnica ha recaído en los Servicios de Farmacia. La calidad de la evidencia no ha demostrado ser una variable decisiva para la aprobación de los tratamientos. En cambio, la edad y el coste sí que han demostrado influir significativamente.

Gonadins, a novel family of glutamyl-tripeptide amides present in the testis with activity in the hypophyseal-gonadal axis.

Here we present a new family of endogenous peptides identified in rat testis with structure of glutamyl-tripeptide amides which are also present in plasma. These peptides have different activities in the hypophyseal-gonadal axis. Evidences showing the endocrine activities of some of the peptides are presented. In this communication we demonstrate the presence of peptides with a common structure Glu-X-Pro amide, where X can be one of the following amino acids: glutamic acid, glutamine, aspartic acid, asparagine, phenylalanine or tyrosine. These peptides have been identified by a series of chromatographies and by mass spectrometry. Some of the peptides where tested for its biological activity observing that subcutaneous administration of the peptides Glu-Glu-Pro amide, Glu-Gln-Pro amide and Glu-Phe-Pro amide were able to reduce plasma levels of testosterone and luteinizing hormone (LH) without modification of the levels of follicle stimulating hormone (FSH). The peptide Glu-Asp-Pro amide, however, produced an increase in the levels of testosterone without modifying LH or FSH levels. It is proposed that the glutamyl-tripeptide amides that reduce the levels of testosterone and LH are released from the testis and act in the pituitary via circulation in an endocrine manner. The specific inhibition of LH release is similar to that produced by inhibin on FSH release. On the other hand the peptide that increases the levels of testosterone is produced in the testis and seems to act directly in the testis in a paracrine or autocrine manner. It is proposed here a new mechanism of regulation of hypophyseal-gonadal axis, a negative feedback exerted by the glutamyl-tripeptide amides in the pituitary. Also it is proposed the generic name of gonadins for the novel family of glutamyl-tripeptide amides. We suggest that gonadins could be used in the future as drugs for treatment of different endocrine disorders, hormone-dependent cancer and as contraceptives.