Evaluación de la seguridad de los catéteres de teflón en pacientes diabéticos tipo 1 tratados con infusión subcutánea continua de insulina (ISCI) mediante la determinación de la cetonemia capilar / Safety evaluation of Teflon catheters in type 1 diabetic patients treated with continuous subcutaneous insulin infusion (CSII) by means of blood ketone testing

Introducción: La monitorización de la cetonemia capilar (ß-hidroxibutirato [BHB]), junto con la glucemia, es de gran importancia en la diabetes mellitus, en particular en situaciones especiales (descompensación hiperglucémica, situaciones de cetosis, enfermedades intercurrentes, embarazo) o en pacientes tratados con infusión subcutánea continua de insulina (ISCI). El objetivo de este estudio fue evaluar la seguridad de 3 catéteres de teflón de diferente longitud mediante la determinación de la cetonemia capilar en pacientes diabéticos tipo 1 en terapia con ISCI. Pacientes y métodos: Seis pacientes con diabetes tipo 1 (duración 21,6 ± 7,4 años), en tratamiento con ISCI (desde 3,1 ± 1,3 años) aceptaron voluntariamente participar en un estudio aleatorizado, secuencial y con diseño cruzado, donde se evaluaron 3 catéteres de teflón (Soft-Set® 9 mm, Quick-Set® 9 mm, y Quick-Set® 6 mm) por períodos de 4 días. Se registraron la glucemia capilar pre y posprandial, y el BHB (BHB sólo los últimos 2 días o en casos de hiperglucemia no esperada) utilizando medidores Optium®. Se consideraron indicativos de cetosis valores de BHB >= 0,5 mmol/l. Resultados: No se observaron diferencias en la glucemia y la cetonemia, basal y total, entre los diferentes tipos de catéter. Tres pacientes presentaron algún valor de cetonemia >= 0,5 mmol/l, lo que obligó al cambio de catéter. La cetonemia capilar y la glucemia media fueron significativamente más elevadas en los pacientes con cetosis frente a los que no la presentaron: 0,10 ± 0,20 frente a 0,01 ± 0,04 mmol/l, y 173 ± 69 frente a 137 ± 63 mg/dl, respectivamente. Asimismo, pudo demostrarse una elevada correlación entre la glucemia y la cetonemia media diarias (r = 0,90), que fue incluso mayor en los casos de cetonemia >= 0,5 mmol/l (r = 0,95). Conclusiones: Los catéteres de teflón de menor longitud (6 mm) no se asocian a un mayor riesgo de cetosis que los catéteres más largos (9 mm). En caso de hiperglucemia, los valores de BHB >= 0,5 mmol/l son indicativos de cetosis y exigen un cambio inmediato del catéter en los pacientes tratados con ISCI

Introduction: Capillary blood ketone testing (ß-hydroxybutyrate, BHB), together with glucose monitoring, is highly important in diabetes care, particularly in special situations (hyperglycemic decompensation, ketosis, intercurrent illnesses or pregnancy) and in patients treated with continuous subcutaneous insulin infusion (CSII). The aim of the present study was to assess the safety of 3 Teflon catheters of different sizes by means of capillary blood ketone testing in type 1 diabetic patients under CSII therapy. Patients and methods: Six patients with type 1 diabetes (diabetes duration: 21.6 ± 7.4 years) under CSII (for 3.1 ± 1.3 years) took part voluntarily in a randomized, sequential and cross-over study designed to evaluate 3 Teflon catheters (Soft-Set® 9 mm, Quick-Set® 9 mm, and Quick-Set® 6 mm) for short periods of 4 days. Pre- and postprandial capillary blood glucose (CBG) and BHB (BHB for the last 2 days only or if there was unexpected hyperglycemia) were measured using Optium® meters. BHB values >= 0.5 mmol/l were considered indicative of ketosis. Results: No differences were found in fasting or total CBG and BHB among the Teflon catheters tested. Three patients showed BHB values >= 0.5 mmol/l requiring a change of catheter. The mean BHB and CBG were significantly higher in patients with ketosis compared with those without: 0.10 ± 0.20 vs 0.01 ± 0.04 mmol/l and 173 ± 69 vs 137 ± 63 mg/dl, respectively. Furthermore, a highly significant correlation was found between mean daily CBG and BHB values (r = 0.90), which were even higher for BHB values >= 0.5 mmol/l (r = 0.95). Conclusions: Short Teflon catheters (6 mm) were not associated with a higher risk of ketosis than longer catheters (9 mm). BHB values >= 0.5 mmol/l in the presence of unexpected hyperglycemia are indicative of ketosis and necessitate an immediate catheter change in type 1 diabetic patients under CSII therapy

Consejos prácticos para la vida diaria con infusión subcutánea continua de insulina (ISCI): ventajas de la determinación de la cetonemia capilar / Practical recomendations for every-day life with continuous subcutaneous insulin infusion (CSII): usefulness of capillary blood ketone test

La monitorización de los cuerpos cetónicos es, junto a la glucemia, de gran importancia en el tratamiento de la diabetes, especialmente de la diabetes tipo 1. La medición de cuerpos cetónicos es necesaria cuando concurren enfermedades intercurrentes o situaciones de estrós, en la hiperglucemia, embarazo o cuando aparecen síntomas de cetoacidosis. En particular, los pacientes diabéticos tipo 1 en tratamiento con infusión subcutánea continua de insulina (ISCI) tienen un mayor riesgo de cetoacidosis. Una interrupción en el suministro de insulina con ISCI se asocia a una rápida alteración del metabolismo, debido al escaso depósito de insulina existente en el tejido subcutáneo. La monitorización de la cetonuria tiene poco valor para el diagnóstico y tratamiento de la cetoacidosis. Las tiras reactivas de cetonuria detectan sólo acetoacetatopero no beta-hidroxibutirato (BHB), el cuerpo cetónico predominante en la cetoacidosis. Además, en la fase de resolución de la cetoacidosis la cetonuria se mantiene incluso elevada mucho tiempo después del descenso de la cetonemia. La cuantificación de BHB con un dispositivo de autodiagnóstico, en 30 segundos, tiene una mayor sensibilidad y permite un diagnóstico más precoz de la cetosis que la cetonuria. Las ventajas asociadas a la determinación de la cetonemia capilar pueden ser relevantes para los pacientes en terapia con ISCI. En la práctica clínica, valores de BHB >= 0,5 mmol/l en presencia de hiperglucemia ó 3 horas después del cambio de catéter, son indicativos de cetosis y, en caso de no ser corregidos, de riesgo de cetoacidosis. La hiperglucemia aislada sin cetonemia elevada (valores de BHB < 0,5 mmol/l) no se asocia a cetosis. En conclusión, la determinación de cetonemia capilar es un complemento importante en la prevención y tratamiento de la cetoacidosis diabética, especialmente en pacientes diabéticos tipo 1 con ICSI

Monitoring of ketone bodies besides of glycemia is important in diabetes care, especially in type 1 diabetes. Ketone testing is recommended during acute intercurrent illness or stress, when blood glucose levels are consistently elevated, during pregnancy or when symptoms of ketoacidosis are present. Type 1 diabetic patients under continuous subcutaneous insulin infusion (CSII) have, particularly, an increased risk of diabetic ketoacidosis. A short interruption of insulin infusion in CSII is associated with a rapid metabolic deterioration, probably due to a limited insulin depot in the subcutaneous tissue. Urine ketone tests are not reliable for diagnosing and/or monitoring treatment of ketoacidosis. Urine ketone tests detect only acetoacetate but not beta- hydroxybuty rate (BHB), the major ketone body in diabetic ketoacidosis. Furthermore, in the recovering phase of diabetic ketoacidosis ketone bodies are still detectable in urine even long after blood ketone concentrations have fallen. Quantification of BHB directly by means of a 30-second hand-held blood ketone meter has a higher sensitivity and provides an earlier diagnosis of ketosis than ketonuria. The advantages related to blood ketone testing may be particularly relevant in patients under CSII therapy. In the clinical practice, BHB values >= 0.5 mmol/l in the presence of unexpected hyperglycemia or 3 h after catheter change are indicative of ketosis and , if not corrected, even impending risk of diabetic ketoacidosis. Isolated hyperglycemia without elevated blood ketone values (i.e. values of BHB < 0.5 mmol/l) is not associated with incipient ketosis. In conclusion, capillary blood ketone testing is an important adjunct to the prevention and treatment of diabetic ketoacidosis, especially in type 1 diabetic patients under CSII

Particularidades de la medición de la glucemia capilar: aspectos técnicos, clínicos y legales / Capillary blood glucose measurement: technical clinical and legal aspects

En la actualidad, se entiende que un control adecuado de la diabetes implica no sólo el seguimiento por parte del personal sanitario, médico o de enfermería, sino que también ha de ser el propio paciente el que realice una vigilancia de sí mismo y de sus hábitos de vida, lo que ha dado lugar al desarrollo de los conceptos de autocontrol y autoanálisis. El desarrollo de una tecnología que facilita la medida de la glucemia pre y posprandial es esencial en el control de la diabetes por el propio sujeto, ya que contribuye tanto a una adecuada administración del tratamiento, como a una apropiada distribución de las ingestas. Desde la aparición, en la década de los ochenta, de los primeros dispositivos de autodiagnóstico, ha habido un gran desarrollo tecnológico, encaminado a facilitar el uso de estos dispositivos a todas las personas en su entorno habitual, es decir, fuera del ámbito puramente sanitario. Manteniendo unas características de precisión y exactitud aceptables según la normativa vigente, los fabricantes han ido buscando una menor posibilidad de error debido a variables que interfieran en la medición, a la vez que se ha ido disminuyendo el volumen de la gota y los tiempos de respuesta. La glucemia capilar tiene hoy en día un importante valor diagnóstico y la fiabilidad con que se consideran sus resultados es innegable. Sin embargo, existen ciertos parámetros que pueden influir en la medición de la glucemia capilar, que conviene considerar, como son el volumen de la gota de sangre, sustancias que interfieren en la medición, rango de hematocrito, tipo de sangre aplicada, tiempo desde la ingesta, calibración del propio medidor, así como ciertos factores ambientales, como la temperatura, la humedad o la altitud. Por ello, para conocer en profundidad qué hay detrás de un cierto valor de glucemia dado por un dispositivo de autodiagnóstico, es necesario profundizar en los aspectos técnicos, clínicos e incluso legales que son aplicables a estos sistemas (AU)

Pharmacological modulation of adrenal medullary GABAA receptor: consistent with its subunit composition.

1. Muscimol, the specific GABAA receptor agonist, increased the secretion of catecholamines by chromaffin cells with an EC50 of 2.9 +/- 0.4 microM. 2. GABAA receptors of these cells were modulated by the same drugs which modulate GABAA receptors in brain tissue. 3. Benzodiazepines enhanced muscimol-evoked catecholamine secretion by between 20 and 80%. This effect seems to be mediated by binding to a central type of benzodiazepine receptor because it was completely blocked by the specific antagonist, Ro 15 1788. This antagonist was able to displace [3H]-flunitrazepam binding with an EC50 of 0.26 +/- 0.05 nM. 4. beta-Carbolines weakly inhibited muscimol-induced catecholamine secretion and were able to displace [3H]-flunitrazepam binding with an EC50 between 0.2 and 0.9 nM, depending on the beta-carboline used. 5. Pregnanolone and related neuroactive steroids enhanced muscimol-evoked catecholamine secretion by up to 87%, in a dose-dependent fashion. In contrast pregnenolone weakly inhibited muscimol-evoked catecholamine secretion. 6. Zn2+ did not affect GABAA receptor-induced catecholamine secretion. 7. These pharmacological results are absolutely concordant with the theoretical properties given by the GABAA receptor subunit composition of bovine adrenal medulla -alpha 1, alpha 4, beta 1-3, gamma 2-previously characterized by Western blot analysis.

GABAB receptors increase intracellular calcium concentrations in chromaffin cells through two different pathways: their role in catecholamine secretion.

The activation of GABAB receptors of adrenal chomaffin cells produces an increase of [Ca2+]i measured by fura-2 AM techniques. GABAB agonists 3-aminopropylphosphinic acid or (-)baclofen, at concentrations of 0.5 mM, increased basal Ca2+ values 332 +/- 60.9 and 306 +/- 40.5 nM, respectively, in cells suspended in a 2.5 mM Ca2+ buffer. The GABAB-induced increase of [Ca2+]i seemed to have two different components. The first was due to an entry from the extracellular medium mainly through L-type voltage-dependent Ca2+ channels as the dihydropiridine nifedipine 50 microM was able to decrease it more than 60%, while omega-conotoxin, which blocks N-type channels, did not produce any change in the GABAB-evoked Ca2+ increment. The second component was due to a release of Ca2+ from intracellular pools and was about one-third of the total GABAB-induced increase of [Ca2+]i. GABAB receptors stimulated inositol 1,4,5-trisphosphate-sensitive and not the caffeine-sensitive Ca2+ store. In a low-Ca2+ buffer after treatment with 2 microM angiotensin II, neither 0.5 mM 3-APPA nor baclofen were able to produce an additional increase of [Ca2+]i, whereas 4 mM caffeine had no effect on GABAB response. This intracellular Ca2+ mobilization could be due to inositol 1,4,5-trisphosphate accumulation produced by the activation of GABAB receptors. In fact, the specific agonists after 10 minutes incubation produced a dose-dependent increase of inositol 1,4,5-trisphosphate. The maximal effect was obtained at 100 microM baclofen and 3-APPA, and it was 3.63 +/- 0.75 and 3.2 +/- 1.5 times the basal levels (7.3 +/- 0.3 pmol/10(6) cells), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

A reassessment of the modulatory role of cyclic AMP in catecholamine secretion by chromaffin cells.

1. The role of adenosine 3':5'-cyclic monophosphate (cyclic AMP) in the regulation of catecholamine (CA) secretion in chromaffin cells remains equivocal from previous studies. 2. In the present study the effect of this cyclic nucleotide on basal CA secretion, as well as on intracellular calcium and membrane potential has been examined. 3. Forskolin and the permeable cyclic AMP analogue, 8-(4-chlorphenylthio)-adenosine-3'-5' monophosphate cyclic (pClpcAMP), increased basal CA secretion in a dose-dependent manner. The EC50s were 0.43 +/- 0.10 microM for forskolin and 39 +/- 9 microM for pClpcAMP. Other agonists with adenylate cyclase activity such as stimulants of adenosine receptors, beta-adrenoceptors, GABAB receptors and intestinal vasoactive peptide (VIP), also increased basal CA secretion in a highly significant manner. However, when they were added together with forskolin, CA secretion was not affected although an additive increase in cyclic AMP levels was produced. 4. Statistical analysis of the correlation between cyclic AMP levels and CA secretion evoked by these cyclic AMP increasing compounds showed that a significant direct correlation between both parameters existed only when low levels of cyclic AMP were produced by secretagogue stimulation. When the increase in intracellular cyclic AMP concentrations exceeded approximately 8 times the basal cyclic AMP levels the correlation was not significant. These results indicate a dual dose-dependent effect of cyclic AMP on basal CA secretion. 5. The stimulatory effect of low cyclic AMP on basal CA secretion was accompanied by an increase in membrane potential and in intracellular calcium concentrations ([Ca2+]j), the latter mainly being due to an increase in intracellular Ca2+ entry through L-type voltage-dependent Ca2" channels.6. The possible mechanisms involved in these cyclic AMP effects are discussed.

Nitric oxide implication in the control of neurosecretion by chromaffin cells.

In this work, we have studied the effects of pure nitric oxide (NO) on the regulation of catecholamine (CA) secretion by chromaffin cells, as well as the possible presence of its synthesizing enzyme L-arginine:NO synthase (NOS) in these cells. Our results show that NO produces a large stimulation of basal CA secretion. This effect was calcium- and concentration-dependent (EC50 = 64 +/- 8 microM) and was not due to nonspecific damage of the tissue by NO. NO also modulates the CA secretion evoked by nicotine in a dose-dependent manner. Although it has a stimulatory effect on the CA secretion evoked by low doses of nicotine (< 3 microM; EC50 = 16 +/- 3 microM), it produces a dose-dependent inhibition of the CA secretion induced by high doses of nicotine (> or = 30 microM; IC50 = 52 +/- 6 microM). The mechanism by which NO modulates CA secretion seems to be through the increase in the cyclic GMP levels, because there was a close correlation between the CA secretion and the cyclic GMP levels. The presence of a specific activity of NOS in chromaffin cells has been demonstrated by two independent methods: release of [14C]citrulline from [14C]arginine and formation of an NO-hemoglobin complex. NOS activity was about 0.5 pmol/min/mg of protein. It was calcium- and mainly calmodulin-dependent and could be specifically blocked by the NOS inhibitor N-methyl-L-arginine. These results suggest that NO could be an important intracellular messenger in the regulation of neurosecretion in chromaffin cells.

Identification of GABAA receptor subunits expressed in bovine adrenal medulla.

The GABAA receptor subunits expressed in adrenal medulla have been characterized by radioligand binding and by immunological methods. The receptors were purified by both benzodiazepine affinity chromatography and anti-alpha 1 413-429 GABAA receptor antibody immunoaffinity chromatography. These preparations were screened by immunoblotting using GABA receptor alpha subunit sequence-specific antibodies. Results showed the existence of the alpha 1 subunit. Thus, the GABAA receptors expressed in adrenal medulla are homogeneous with respect to their alpha subunit complement and consistent with type BZ1 benzodiazepine receptor pharmacology.

GABAB receptors modulate catecholamine secretion in chromaffin cells by a mechanism involving cyclic AMP formation.

1. The function of gamma-aminobutyric acidB (GABAB) receptors in modulation of catecholamine secretion by chromaffin cells and the possible mechanism involved in this action have been examined. 2. The GABAB agonists (-)-baclofen and 3-aminopropylphosphinic acid (3-APPA) were found to induce a dose-dependent increase of basal catecholamine secretion. The EC50s were 151 +/- 35 microM and 225 +/- 58 microM for baclofen and 3-APPA, respectively. This stimulatory effect was specific since it could be blocked by 0.5 mM of the specific GABAB antagonist CGP-35348. 3. In contrast, preincubation of chromaffin cells with the GABAB agonists was found to inhibit, in a dose-dependent manner, the catecholamine secretion evoked by 10 microM nicotine and 200 microM muscimol. 4. The effects of GABAB agonists on both basal and evoked catecholamine secretion were found to be accompanied by parallel changes in intracellular calcium concentration ([Ca2+]i). GABAB agonists produced a dose-dependent increase in [Ca2+]i which was partially blocked by CGP 35348, but they produced a strong inhibition of the [Ca2+]i increase induced by nicotine and muscimol. 5. The GABAB agonists also produced a dose-dependent increase in intracellular cyclic AMP levels, there being a direct correlation between both increase in catecholamine secretion and in intracellular cyclic AMP levels. 6. The pretreatment of chromaffin cells with pertussis toxin doubled the catecholamine secretion and increased by four times the intracellular cyclic AMP levels evoked by GABAB agonists. 7. The possible involvement of adenylate cyclase in the mechanism of GABAA receptor modulation of catecholamine secretion is discussed.

Mechanism through which GABAA receptor modulates catecholamine secretion from bovine chromaffin cells.

The actions and mechanism of GABAergic modulation of catecholamine secretion from isolated bovine chromaffin cells were investigated. The GABAA receptor agonist muscimol induced a fast rise in cytosolic [Ca2+]. The mean peak increase was 290 +/- 30 nM over basal levels. The increase in cytosolic [Ca2+] was abolished in the absence of extracellular [Ca2+] and was blocked by the GABAA antagonist bicuculline and the dihydropiridine nifedipine. Muscimol also elicited the release of catecholamines and increased the bisoxonol fluorescence indicating a cell depolarization. The [Ca2+] entry was well correlated with muscimol-evoked catecholamine secretion. When cells were treated with muscimol and a second secretagogue, a biphasic behavior was revealed. Muscimol enhanced the catecholamine release evoked by low concentrations of nicotine or K+, whereas release obtained at high concentrations of nicotine or K+ was actually inhibited. When the muscimol effect on membrane potential was studied in the presence of low K+ or nicotine concentrations, an enhancement of the bisoxonol fluorescence was observed. This effect was reversed at high concentrations of both K+ and nicotine. Measurement of 36Cl- fluxes showed an increase in membrane permeability to Cl- during muscimol stimulation. The influx or efflux in Cl- was dependent on membrane potential. In normal conditions, with a K+ concentration of 5.4 mM, a Cl- efflux was observed by both radiometric techniques, with 36Cl- and by the use of the chloride-sensitive fluorescent probe 6-methoxy-N-(3-sulphopropil)quinolinium, as indicator of intracellular Cl-. At high nicotine (20 mM) or K+ concentrations (105 mM) a Cl- influx was observed using 6-methoxy-N-(3-sulphopropil)quinolinium.(ABSTRACT TRUNCATED AT 250 WORDS)