Monitorización farmacocinética de antagonistas del factor de necrosis tumoral: utilidad clínica en enfermedad inflamatoria intestinal / Pharmacokinetics monitoring of tumour necrosis factor inhibitors: utility in inflammatory bowel disease management

Introducción: El fracaso de la terapia con biológicos en la enfermedad inflamatoria intestinal (EII) es un problema común. La monitorización farmacocinética es una herramienta que podría permitir optimizar estos tratamientos mediante la individualización de la posología en los diferentes escenarios clínicos. Objetivo: Describir las determinaciones de concentraciones séricas de infliximab y adalimumab en pacientes con EII y evaluar el impacto de las recomendaciones farmacocinéticas en la toma de decisiones clínicas y la evolución de los pacientes.Métodos: Estudio trasversal observacional retrospectivo de dos años de duración (2017-2018) de las determinaciones de inhibidores del factor de necrosis tumoral (anti-TNF) realizadas en pacientes del Servicio de Medicina Digestiva de un hospital general. Resultados: Se realizaron 133 determinaciones correspondientes a 66 sujetos (38% tratados con adalimumab; 62% infliximab). El principal motivo de monitorización (>55%) fue la presencia de enfermedad activa. Más de la mitad de los pacientes tenían concentraciones fuera del intervalo terapéutico (el 51% de adalimumab y 37% de infliximab presentaban una exposición subóptima). La recomendación de mantener la pauta posológica previa se propuso en <40% de los informes farmacocinéticos, siendo el grado de aceptación de la recomendación superior al 80% en todos los casos. Los datos analíticos de inflamación se redujeron tras la monitorización sin mostrar significación estadística en todos los casos.Conclusión: La mayoría de pacientes con EII tratados con anti-TNF presentan concentraciones de fármaco inadecuadas. La monitorización ha demostrado ser una herramienta útil para guiar la toma de decisiones terapéuticas y podría contribuir en la mejora de los parámetros clínicos de estos pacientes. (AU)

Introduction: The failure of biologic therapy in inflammatory bowel disease (IBD) is a common problem. The pharmacokinetic monitoring is a useful tool that allows to optimize these treatments.Objective: To describe the pharmacokinetic determinations of plasma concentrations of infliximab and adalimumab in patients with IBD and evaluate its impact on clinical decision.Method: Retrospective, observational study of two years duration (2017-2018) of the tumor necrosis factor (anti-TNF) inhibitor determinations performed in patients of the Digestive Service of a general hospital.Results: A total of 133 determinations were obtained about 66 subjects (38% adalimumab, 62% infliximab). The main reason (>55%) of the request for monitoring was the presence of active disease. More than half of the patients had concentrations outside the therapeutic range (51% of patients with adalimumab and 37% of those with infliximab had plasma levels below the lower range considered suboptimal). The maintenance of the previous dosage was recommended only in <40% of the monitoring and the degree of acceptance of the interventions were more than 80% in all cases. The analytical data of inflammation were reduced after monitoring without showing statistical significance in all cases.Conclusion: Standard anti-TNF regimen was not adequate to obtain range concentrations in more than half of analyzed cases. Monitoring has proven to be very useful in supporting clinical decision and it may promote an improvement in the clinical parameters of patients with IBD. (AU)

Resistencia Bacteriana a desinfectantes en áreas comunes de oficinas / Bacterial Resistance to disinfectants in common office areas

Introducción. El uso de diferentes agentes químicos para la atenuación, tratamiento y control de microorganismos ha venido aumentando, la falta de control y conocimiento de estos productos, está generando un cambio del genoma en los microorganismos, provocando resistencia a concentraciones normales de biocidas. Objetivo: Realizar una revisión sistemática sobre la resistencia bacteriana a los desinfectantes en áreas comunes de oficina. Métodos: Revisión sistemática de bases de datos; Scielo, Elsevier, Pubmed y ACS Publications research, y fuentes secundarias como la OPS (organización Panamericana de la Salud) y la OMS (Organización Mundial de la Salud), entre otras, utilizando términos tales como; Resistencia bacteriana, desinfección, enfermedades laborales o profesionales y resistencia a desinfectantes. Resultados: Enterobacter sp. resistente a Amonio Cuaternario (QAC), desinfectantes a base de halógeno y formaldehído al 37%; Pseudomonas aeruginosa 71% de los aislamientos multirresistentes a los antibióticos, 43% susceptibilidad reducida a QAC, a triclosan (TC) y Benzalconio (BAC), y 24 aislamientos resistentes a agentes antimicrobianos. M. massiliense BRA 100 susceptible a ortoftaldehido (OPA), ácido peracético (PA), y a altas concentraciones de glutaraldehído. Aislamientos clínicos de cepas multirresistentes a antibióticos como: MRSA, Enterococcus sp. y Pseudomonas aeruginosa, 52% y 38% cepas fueron resistentes a compuestos de amonio cuaternario y fenol, respectivamente. Conclusiones: La presencia de microorganismos resistente en lugares comunes como; pisos, interruptores de luz, manijas de puertas, escritorios y sillas, entre otras, enuncia un problema de salud pública que se debe comenzar a tratar, cambiando las metodologías utilizadas para la desinfección, y otras medidas de control y prevención.

Introduction. The use of different chemical agents for the attenuation, treatment and control of microorganisms has been increasing, the lack of control and knowledge of these products is generating a change in the genome in microorganisms, causing resistance to normal concentrations of biocides. Objective: To carry out a systematic review on bacterial resistance to disinfectants in common office areas. Methods: Systematic review of databases; Scielo, Elsevier, Pubmed and ACS Publications research, and secondary sources such as PAHO (Pan American Health Organization) and WHO (World Health Organization), among others, using terms such as; Bacterial resistance, disinfection, occupational or professional diseases and resistance to disinfectants. Results: Enterobacter sp.: resistant to Quaternary Ammonium (QAC), halogen-based disinfectants and 37% formaldehyde; Pseudomonas aeruginosa: 71% of isolates multiresistant to antibiotics, 43% reduced susceptibility to QAC, triclosan (TC) and Benzalkonium (BAC), and 24 isolates resistant to antimicrobial agents. M. massiliense BRA 100 susceptible to orthophthaldehyde (OPA), peracetic acid (PA), and high concentrations of glutaraldehyde. Clinical isolates of multiresistant strains to antibiotics such as: MRSA, Enterococcus sp. and Pseudomonas aeruginosa, 52% and 38% strains were resistant to quaternary ammonium and phenol compounds, respectively. Conclusions: The presence of resistant microorganisms in common places such as; floors, light switches, door handles, desks and chairs, among others, enunciates a public health problem that must begin to be addressed, changing the methodologies used for disinfection, and other control and prevention measures.

Conocimiento e investigación sobre la autonomía profesional en enfermería. Revisión narrativa / Knowledge and research about nursing professional autonomy. Narrative review / Conhecimento e pesquisa sobre autonomia profissional em enfermagem. Revisão narrativa

Introducción: Enfermería como disciplina se encuentra en un momento trascendental a la luz de los desarrollos científicos que están en espera de ser incorporados en el cuidado y que necesitan enfermeros autónomos en su práctica profesional, por lo cual en el presente trabajo se realizó una revisión narrativa del concepto de autonomía. Objetivo: Describir el concepto, medición e investigaciones sobre la autonomía profesional en estudiantes de enfermería. Desarrollo: La autonomía profesional ha acompañado la evolución de la enfermería; ha pasado por momentos de invisibilidad hasta ser parte de la definición de la profesión y su práctica. Por lo anterior, la medición de este constructo ha cobrado gran importancia, identificándose tres categorías, en primer lugar se encuentran los instrumentos que buscan explorar la actitud de la enfermera y las características de los pacientes, en segundo lugar, los que fijan su perspectiva desde el desempeño laboral de la enfermera y por último se destacan aquellos que hacen una diferenciación de la medición según características como sexo y experticia; estos instrumentos han sido empleados en estudios principalmente transversales que han establecido comparaciones con otras profesiones. Conclusiones: Dada la importancia del concepto de autonomía y su escasa descripción, medición y evaluación como constructo de la identidad profesional en enfermería, así como la escasez de trabajos publicados en español; se identificó la necesidad de realizar investigaciones con instrumentos válidos, en diseños longitudinales que establezcan los factores asociados al desarrollo de la autonomía profesional y contribuyan al fortalecimiento de esta característica en el personal de enfermería.

Introduction: The discipline of Nursing is situated in a transcendental moment because, among other, the scientific developments which are being incorporated into the healthcare process are to be utilized by autonomous nurses. Thus, this study is aimed at narratively reviewing the concept of autonomy. Objective: To describe the concept, measurement, and related research, regarding professional autonomy among nursing students. Development: Professional autonomy has accompanied the evolution of nursing from, at some points being invisible, to now being an explicit part of the profession's definition and practice. Because of this, the construct's measurement has become more important. Three types of instruments have been suggested: those with a focus in the exploration of attitudes of nurses and patients; those with a perspective towards the nurses' performance; and those based on specific characteristics such as sex and expertise. These instruments have been mainly used in transversal studies for comparisons. Conclusions: Given the importance of the concept, considering the scant information related to the description, measurement, and assessment as a nursing professional identity construct, and also considering the scant Spanish-published related studies, a need was identified to do research with longitudinal designs and validated instruments which can reveal the factors associated with the development and strengthening of professional autonomy in nursing personnel.

Introdução: A enfermagem como disciplina encontra-se em um momento transcendental à luz dos desenvolvimentos científicos que estão na espera de ser incorporados no cuidado, e que necessitam enfermeiros autônomos em sua prática profissional, pelo qual no presente trabalho realizou-se uma revisão narrativa do conceito de autonomia. Objetivo: Descobrir o conceito, medição e pesquisas sobre a autonomia profissional em estudantes de enfermagem. Desenvolvimento: A autonomia profissional tem acompanhado a evolução da enfermagem; tem passado por momentos de invisibilidade até ser parte da definição da profissão e sua prática. Portanto, a medição deste construto cobrou grande importância, identificando-se três categorias, em primeiro lugar encontram-se os instrumentos que buscam explorar a atitude da enfermeira e as características dos pacientes, em segundo lugar, os que fixam sua perspectiva desde o desempenho laboral da enfermeira e por último destacam-se aqueles que fazem uma diferenciação da medição segundo características como sexo e expertise; estes instrumentos têm sido empregados em estudos principalmente transversais que estabeleceram comparações com outras profissões. Conclusões: Dada a importância do conceito de autonomia e sua escassa descrição, medição e avaliação como constructo da identidade profissional em enfermagem, assim como a escassez de trabalhos publicados em espanhol; identificou-se a necessidade de realizar pesquisas com instrumentos válidos, em desenhos longitudinais que estabeleçam os fatores associados ao desenvolvimento da autonomia profissional e contribuam no reforço desta característica no pessoal de enfermagem.

A rapid validated UV-HPLC method for the simultaneous determination of the antiretroviral compounds darunavir and raltegravir in their dosage form.

OBJECTIVE: A rapid, simple and sensitive high-performance liquid chromatography (HPLC) method with ultraviolet detection has been developed for quantification of darunavir and raltegravir in their pharmaceutical dosage form. METHODS: The assay enables the measurement of both drugs with a linear calibration curve (R2= 0.999) over the concentration range 5-100 mg/L. The determination was performed on an analytical Tracer Excel 120 ODSB (15x0.4.6 cm) column at 35ºC. The selected wavelength was 254 nm. The mobile phase was a mixture of 0.037 M sodium dihydrogen phosphate buffer, acetonitrile and methanol (40:50:10, v/v/v) at a flow rate of 2.0 mL/min Nevirapine (50 mg/L) was used as internal standard. RESULTS: Accuracy, intra-day repeatability (n = 5), and inter-day precision (n = 3) were found to be satisfactory, being the accuracy from -4.33 to 3.88% and precisions were intra-day and inter-day, 0.25% and 4.42% respectively in case of darunavir. Raltegravir intra-day and inter-day precisions lower of 1.01 and 2.36%, respectively and accuracy values bet from -4.02 to 1.06%. CONCLUSIONS: Determination of the darunavir and raltegravir in their dosage form was done with a maximum deviation of 4%. This analytical method is rapid, easily implantable and offers good results.

Antibacterial effect of sevoflurane and isoflurane.

OBJECTIVE: Multidrug resistant bacteria are increasing worldwide and therapeutic options are limited. Some anaesthetics have shown antibacterial activity before. In this study, we have investigated the antibacterial effect of the halogenated anaesthetic agents sevoflurane and isoflurane against a range of resistant pathogens. METHODS: Two experiments were conducted. In the first, bacterial suspensions of both ATCC and resistant strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa were exposed to liquid sevoflurane and isoflurane during 15, 30 and 60 minutes. In the second experiment clinical resistant strains of E. coli, Klebsiella pneumoniae, Enterobacter cloacae, P. aeruginosa, Acinetobacter baumannii, S. aureus, and Enterococcus faecium were studied. Previously inoculated agar plates were irrigated with the halogenated anaesthetic agents and these were left to evaporate before the plates were incubated. In both experiments colony forming units were counted in resultant plates. RESULTS: In the first experiment, isoflurane showed faster and higher antimicrobial effect than sevoflurane against all the strains studied. Gram-negative organisms were more susceptible. In the second experiment, E. faecium was found to be resistant to both halogenated agents; only isoflurane showed statistically significant activity against the rest of the strains studied. CONCLUSIONS: Both halogenated agents, but particularly isoflurane, showed in vitro antibacterial activity against pathogens resistant to conventional antibiotics. Further investigation is required to determine whether or not they also exhibit this property in vivo. This might then allow these agents to be considered as rescue treatment against multidrug resistant pathogens, including a topical use in infected wounds.

"Melioidosis in Antioquia, Colombia: an emerging or endemic disease? A cases series".

BACKGROUND: Melioidosis is endemic in Malaysia, the southwest of Thailand, and northern Australia. The incidence in Thailand is 4.4/1000000 inhabitants, where it causes 19% of community-acquired pneumonia (CAP) and 20% of bacteremic pneumonia, and the mortality is 50%. Sporadic cases have been described in Central and South America. The objective of this study was to describe the clinical and epidemiological features and ecological characteristics of melioidosis in Antioquia, Colombia. METHODS: This is a case series description. RESULTS: Seven cases were identified. Burkholderia pseudomallei was isolated from peripheral blood, pleural fluid, and urine and was identified by the automated system VITEK 2 (bioMérieux) and API 20NE biochemical kit. Five of the cases had a bacteremic form with shock and pulmonary compromise and two of these patients died. The non-bacteremic melioidosis cases had genitourinary, abdominal, and osteoarticular compromise. All patients had comorbidities and lived in rural hot and humid areas in the west central region of Colombia (Antioquia). Diabetes mellitus, renal insufficiency, and other chronic diseases are important risk factors for the development of severe forms. CONCLUSIONS: The cases presented here are similar to those occurring in endemic areas regarding comorbidity, risk factors, clinical presentation, and environmental conditions. It is necessary to establish whether melioidosis is an endemic and under-diagnosed disease or an emerging disease in Colombia.

Alteraciones en el eje hipotálamo-tejido adiposo y su relación con el riesgo para la aterosclerosis coronaria / Alterations in hypothalamus-adipose tissue axis in relation with the risk of coronary atherosclerosis

Recent population studies in Southern Argentina have found a sharp rise in prevalence of overweight and obesity in both sexes and specially after fifty years of age. Hence, the obesity in itself was found associated with the presence of metabolic syndrome (MS) and coronary heart disease, which have been demonstrated by angiography studies. The regulation of energy homeostasis is controlled by interactions between the central nervous system (neurotransmitters and neuropeptides) and the peripheric system (hormones) through very complex mechanisms. Genetics or acquired alterations in these regulation systems can be the origin of obesity and specially of central obesity. The visceral adipose tissue can be considered a secretor organ and its mass increment could generate insulin-resistance (IR) state, which directly or indirectly, could develop into endothelial dysfunction and coronary atherosclerosis. Although some studies estimate that 40% of IR are of genetic origin, a high proportion of these are acquired by inadequate habits in life style (specially excess of food intake and low physical activity). Finally, a better knowledge of the central and peripheric regulations in alimentation habits and energetic balance could help to develop treatments to decrease the incidence of these metabolic alterations and, consequently the morbidity and mortality due to coronary atherosclerosis.

Estudios poblacionales en la región sur de Argentina mostraron una elevada prevalencia de sobrepeso y obesidad en sujetos de ambos sexos, sobre todo luego de los 50 años de edad; laobesidad central se halló fuertemente asociada con la presencia del síndrome metabólico (SM) y con la enfermedadcoronaria demostrada por angiografía. La regulación de la homeostasis de la energía se realiza a travésde la interacción entre el sistema nervioso central (neurotransmisores y neuropéptidos) y el sistema periférico(hormonas) mediante complejos mecanismos. Alteraciones genéticas o adquiridas en estos sistemas deregulación pueden conducir a la obesidad y en especial a la obesidad central. Considerando al tejido adiposovisceral como un órgano secretor, incrementos de su masa pueden generar estados de insulino-resistencia (IR),la cual directa o indirectamente puede conducir a la disfunción endotelial y a la aterosclerosis coronaria. Aunqueun 40% de IR serían de origen genético, una elevada proporción de ellos son adquiridos por conductasinadecuadas en el estilo de vida (exceso de ingesta de calorías y baja actividad física). Un mayor conocimientode la regulación central y periférica de los hábitos alimentarios y del balance energético podría ayudar a desarrollartratamientos para disminuir la incidencia de estas alteraciones metabólicas y con ello la probabilidad deenfermar o morir por enfermedad coronaria.

Alteraciones en el eje hipotálamo-tejido adiposo y su relación con el riesgo para la aterosclerosis coronaria / Alterations in hypothalamus-adipose tissue axis in relation with the risk of coronary atherosclerosis

Recent population studies in Southern Argentina have found a sharp rise in prevalence of overweight and obesity in both sexes and specially after fifty years of age. Hence, the obesity in itself was found associated with the presence of metabolic syndrome (MS) and coronary heart disease, which have been demonstrated by angiography studies. The regulation of energy homeostasis is controlled by interactions between the central nervous system (neurotransmitters and neuropeptides) and the peripheric system (hormones) through very complex mechanisms. Genetics or acquired alterations in these regulation systems can be the origin of obesity and specially of central obesity. The visceral adipose tissue can be considered a secretor organ and its mass increment could generate insulin-resistance (IR) state, which directly or indirectly, could develop into endothelial dysfunction and coronary atherosclerosis. Although some studies estimate that 40% of IR are of genetic origin, a high proportion of these are acquired by inadequate habits in life style (specially excess of food intake and low physical activity). Finally, a better knowledge of the central and peripheric regulations in alimentation habits and energetic balance could help to develop treatments to decrease the incidence of these metabolic alterations and, consequently the morbidity and mortality due to coronary atherosclerosis.(AU)

Estudios poblacionales en la región sur de Argentina mostraron una elevada prevalencia de sobrepeso y obesidad en sujetos de ambos sexos, sobre todo luego de los 50 años de edad; laobesidad central se halló fuertemente asociada con la presencia del síndrome metabólico (SM) y con la enfermedadcoronaria demostrada por angiografía. La regulación de la homeostasis de la energía se realiza a travésde la interacción entre el sistema nervioso central (neurotransmisores y neuropéptidos) y el sistema periférico(hormonas) mediante complejos mecanismos. Alteraciones genéticas o adquiridas en estos sistemas deregulación pueden conducir a la obesidad y en especial a la obesidad central. Considerando al tejido adiposovisceral como un órgano secretor, incrementos de su masa pueden generar estados de insulino-resistencia (IR),la cual directa o indirectamente puede conducir a la disfunción endotelial y a la aterosclerosis coronaria. Aunqueun 40% de IR serían de origen genético, una elevada proporción de ellos son adquiridos por conductasinadecuadas en el estilo de vida (exceso de ingesta de calorías y baja actividad física). Un mayor conocimientode la regulación central y periférica de los hábitos alimentarios y del balance energético podría ayudar a desarrollartratamientos para disminuir la incidencia de estas alteraciones metabólicas y con ello la probabilidad deenfermar o morir por enfermedad coronaria.(AU)

La comprensión escrita de preposiciones y partículas interrogativas: un estudio en sujetos sordos / No disponible

El objetivo de este estudio fue profundizar en los problemas de comprensión lectora que padecen los sujetos sordos. Para ello fueron elegidos dos tipos de palabras: preposiciones y partículas interrogativas, ambas muy frecuentes en los textos y decisivas para la correcta comprensión de las frases. Cada categoría fue evaluada a través de 55 items. La muestra estuvo formada por 40 personas sordas de entre 13 y 58 años, utilizándose para establecer los diferentes subgrupos los siguientes factores: edad, momento de la pérdida auditiva, grado de la misma y sistema de comunicación utilizado. Un grupo de niños oyentes de 7 y 8 años sirvió de grupo de control. Los resultados ponen de manifiesto los problemas que los sordos tienen para comprender ambos tipos de palabras, así como diferencias entre los distintos subgrupos de sordos (AU)

The aim of this study was to examine the reading comprehension problems in deaf people. Two kind of words were chosen to analyse these problems: prepositions and interrogative particles, both being very frequently found in texts and essential in the correct understanding of a sentence. Each category was evaluated with 55 items. 40 deaf people between 13 and 58 years old took part in this research. Age, moment in which hearing loss took place, degree of hearing loss and communication system were used as independent variables, and used to classify them. A group of non-deaf children aged 7 and 8 acted as control. The results show the existence of significant differences between the different subgroups indicating the difficulties that deaf people has in understanding both, prepositions and interrogative particles (AU)

Etanolemia y etilometría: un punto de discusión / Ethanolaemia and ethylometry: a point of controversy

El etanol es causa directa de muchos accidentes de circulación.Los efectivos policiales emplean la determinación de alcohol etílico en aire expirado mediante etilómetros de precisión como medida indirecta para conocer la concentración de etanol en sangre.Nuestro estudio pretende comparar la etilometría con la determinación directa de la concentración de etanol en sangre a partir de muestras de suero mediante un método enzimático, así como conocer la concentración de alcohol etílico en una muestra en el momento de su extracción y tras diez días de congelación.Los resultados muestran que no existe buena correlación entre etilometría o medida de etanol en aire expirado y la medida directa en sangre mediante método enzimático. Por otra parte, la congelación se presenta como un método adecuado de transporte y conservación de las muestras que contienen alcohol etílico, hecho ya demostrado en trabajos anteriores. (AU)

Viscosuplementacion: revisión de los diferentes hialuronatos en España / Viscosupplementation: review of hyaluronic acids in Spain

En el presente trabajo procedemos a revisar y comparar las propiedades de seis viscoelásticos compuestos por ácido hialurónico o derivados comercializados en España como productos sanitarios (implantes clínicos, clase III) y de cada vez mayor aplicación en patología degenerativa por osteoartrosis, principalmente de rodilla. Concluimos con la posible recomendación de abordar estos productos desde el punto de vista farmacológico aunque estén registrados como producto sanitario. Asimismo son necesarios mayor número de trabajos y estudios más específicos que en un primer lugar comparen entre sí los distintos productos comercializados y que en un segundo lugar refuercen sus ventajas e inconvenientes en la práctica clínica diaria (AU)

Hormonal regulation of 5alpha-reductase activity in rat epididymis.

The specific activity of epididymal 5alpha-reductase (pmol 5alpha-reduced products mg protein-1 h-1) decreased by 17, 44, 58 and 83% of the initial value and its total activity (nmol 5alpha-reduced products organ-1 h-1) decreased by 66, 85, 94 and 98% 2, 4, 8 and 14 days respectively, after castration. The loss of total activity always exceeded the decrease in organ weight and protein content. The decline in enzymic activity could be prevented by implantation of testosterone at the time of castration. Administration of testosterone propionate (200 microgram/day) for 12 days starting 1 month after castration was associated with the weights of the accessory organs returning to the control values and although the specific activity of 5alpha-reductase was almost completely restored by this treatment, the total activity of the nuclear fraction remained at 49% of the control value. Recombination experiments demonstrated that the effect of androgens is not mediated by a factor present in the soluble fraction and the concomitant administration of androgen and either cycloheximide or actinomycin D blocked the effect of androgen. These data suggest that androgens stimulate the synthesis of epididymal 5alpha-reductase.

Partial characterization of epididymal 5 alpha reductase in the rat.

Epididymal 5alpha reductase activity was found distitributed in the crude nuclear fraction (44 percent) and microsomal fraction (41 percent). Spermatozoa contaminating the nuclear preparation accounted for only 3 percent of its activity. There were no regional differences in the distribution of total 5alpha reductase activity. However, the nuclear enzyme was more active in caput than in other regions. Maximal activity was found at pH 6.2 and at 32 degrees C. Both enzymes had an absolute requirement of reduced dinucleotides. The microsomal preparation could only us NADPH while the nuclear enzyme could use NADPH and NADH. The apparent Km for the microsomal preparation was 0.62 +/- 0.05 X 10(-6)M and Vmax was 555 +/- 38 pmoles/mg protein/hour. The nuclear enzyme presented similar values. The reaction was not inhibited by accumulation of product in the medium, but other steroids such as progesterone, epitestosterone (17alpha-hydroxy-4-androsten-3-one) and 3-oxo-4-androstene-17beta-carboxylic acid were potent competitive inhibitors. The reaction was strongly inhibited by Hg, Zn and Cu. The properties of the epididymal reductase are similar to those of the prostatic enzyme.