Optimización de los aislamientos preventivos en una UCI polivalente mediante la aplicación de un plan de intervención / Optimization of pre-emptive isolations in a polyvalent ICU through implementation of an intervention strategy

ANTECEDENTES: El aislamiento preventivo consiste en la aplicación de medidas de aislamiento de contacto en pacientes con alta sospecha de estar colonizados por bacterias multirresistentes. OBJETIVO: Evaluar el impacto de un programa de intervención basado en la implantación de un Protocolo Consensuado de Aislamiento Preventivo (PCAP) al ingreso en una UCI polivalente de un hospital general. MÉTODO: Análisis comparativo de 2 cohortes de pacientes, una histórica, que incluye pacientes a los que se indicó el aislamiento preventivo a juicio del médico responsable (enero de 2010 a febrero de 2011), y otra prospectiva, que incluye los pacientes a los que se aplicó el PCAP (marzo a noviembre de 2011). El PCAP incluyó la identificación y divulgación de los criterios de aislamiento preventivo, la metodología a seguir en cuanto a toma de muestras, la valoración de los resultados y los criterios de retirada del aislamiento. La indicación del aislamiento fue realizada por el personal médico, y un equipo de enfermería realizó el seguimiento. Se definió el aislamiento preventivo como «adecuado» cuando en alguna de las muestras iniciales se identificó una bacteria multirresistente. Para la comparación de resultados entre los 2 periodos se utiliza la chi cuadrado para variables cualitativas y la t de Student para variables cuantitativas. Se aceptan como significativas diferencias con p < 0,05. RESULTADOS: De los 1.740 pacientes ingresados en UCI (1.055 en el primer periodo y 685 en el segundo) se indicó el aislamiento preventivo en 199 (11,4%), de los que 111 (10,5%) correspondieron a la fase histórica (grupo control) y 88 (12,8%) a la fase posterior a la implantación del PCAP (grupo de intervención). No se han detectado diferencias en la edad, el APACHE II y las características de los pacientes entre los 2 periodos. La aplicación del PCAP se ha relacionado con una disminución de los aislamientos preventivos no indicados (29,7 vs. 6,8%, p < 0,001), una disminución del tiempo en la solicitud de las muestras de vigilancia (1,56 vs. 0,37 días, p < 0,001), y una disminución de la duración en días del aislamiento (4,77 vs. 3,58 días, p < 0,001). En 44 pacientes (22,1%) en los que se indicó el aislamiento preventivo se identificaron más de una bacteria multirresistente, siendo la tasa de «aislamiento preventivo adecuado» del 19,8% en el primer periodo y del 25,0% en el segundo (p < 0,382). CONCLUSIONES: Tras la instauración de PCAP se han reducido significativamente los aislamientos preventivos no indicados correctamente, se ha disminuido el tiempo entre el aislamiento y la toma de muestras, además de reducirse la duración del aislamiento en los casos en que no es necesario, sin que haya aumentado la tasa de «aislamiento preventivo adecuado»

BACKGROUND: Pre-emptive isolation refers to the application of contact precaution measures in patients with strongly suspected colonization by multiresistant bacteria. OBJECTIVE: To assess the impact of an intervention program involving the implementation of a consensus-based protocol of pre-emptive isolation (CPPI) on admission to a polyvalent ICU of a general hospital. METHODS: A comparative analysis of 2 patient cohorts was made: a historical cohort including patients in which pre-emptive isolation was established according to physician criterion prior to starting CPPI (from January 2010 to February 2011), and a prospective cohort including patients in which CPPI was implemented (from March to November 2011). CPPI included the identification and diffusion of pre-emptive isolation criteria, the definition of sampling methodology, the evaluation of results, and the development of criteria for discontinuation of pre-emptive isolation. Pre-emptive isolation was indicated by the medical staff, and follow-up was conducted by the nursing staff. Pre-emptive isolation was defined as "adequate" when at least one multiresistant bacteria was identified in any of the samples. Comparison of data between the 2 periods was made with the chi-square test for categorical variables and the Student t-test for quantitative variables. Statistical significance was set at P < .05. RESULTS: Among the 1,740 patients admitted to the ICU (1,055 during the first period and 685 during the second period), pre-emptive isolation was indicated in 199 (11.4%); 111 (10.5%) of these subjects corresponded to the historical cohort (control group) and 88 (12.8%) to the posterior phase after the implementation of CPPI (intervention group). No differences were found in age, APACHE II score or patient characteristics between the 2 periods. The implementation of CPPI was related to decreases in non-indicated pre-emptive isolations (29.7 vs. 6.8%, P<.001), time of requesting surveillance cultures (1.56 vs. 0.37 days, P<.001), and days of duration of treatment (4.77 vs. 3.58 days, P<.001). In 44 patients (22.1%) in which pre-emptive isolation was indicated, more than one multiresistant bacteria was identified, with an "adequate pre-emptive isolation rate” of 19.8% in the first period and 25.0% in the second period (P<.382). CONCLUSIONS: The implementation of CPPI resulted in a significant decrease in pre-emptive isolations which were not indicated correctly, a decrease in the time elapsed between isolation and collection of samples, and a decrease in the duration of isolation measures in cases in which isolation was unnecessary, without increasing the rate of "adequate pre-emptive isolation"

Optimization of pre-emptive isolations in a polyvalent ICU through implementation of an intervention strategy.

BACKGROUND: Pre-emptive isolation refers to the application of contact precaution measures in patients with strongly suspected colonization by multiresistant bacteria. OBJECTIVE: To assess the impact of an intervention program involving the implementation of a consensus-based protocol of pre-emptive isolation (CPPI) on admission to a polyvalent ICU of a general hospital. METHODS: A comparative analysis of 2 patient cohorts was made: a historical cohort including patients in which pre-emptive isolation was established according to physician criterion prior to starting CPPI (from January 2010 to February 2011), and a prospective cohort including patients in which CPPI was implemented (from March to November 2011). CPPI included the identification and diffusion of pre-emptive isolation criteria, the definition of sampling methodology, the evaluation of results, and the development of criteria for discontinuation of pre-emptive isolation. Pre-emptive isolation was indicated by the medical staff, and follow-up was conducted by the nursing staff. Pre-emptive isolation was defined as "adequate" when at least one multiresistant bacteria was identified in any of the samples. Comparison of data between the 2 periods was made with the chi-square test for categorical variables and the Student t-test for quantitative variables. Statistical significance was set at P<.05. RESULTS: Among the 1,740 patients admitted to the ICU (1,055 during the first period and 685 during the second period), pre-emptive isolation was indicated in 199 (11.4%); 111 (10.5%) of these subjects corresponded to the historical cohort (control group) and 88 (12.8%) to the posterior phase after the implementation of CPPI (intervention group). No differences were found in age, APACHE II score or patient characteristics between the 2 periods. The implementation of CPPI was related to decreases in non-indicated pre-emptive isolations (29.7 vs. 6.8%, P<.001), time of requesting surveillance cultures (1.56 vs. 0.37 days, P<.001), and days of duration of treatment (4.77 vs. 3.58 days, P<.001). In 44 patients (22.1%) in which pre-emptive isolation was indicated, more than one multiresistant bacteria was identified, with an "adequate pre-emptive isolation rate" of 19.8% in the first period and 25.0% in the second period (P<.382). CONCLUSIONS: The implementation of CPPI resulted in a significant decrease in pre-emptive isolations which were not indicated correctly, a decrease in the time elapsed between isolation and collection of samples, and a decrease in the duration of isolation measures in cases in which isolation was unnecessary, without increasing the rate of "adequate pre-emptive isolation".

Superfusion of synaptosomes to study presynaptic mechanisms involved in neurotransmitter release from rat brain.

Neurotransmitter release, as the primary way for neuron signaling, represents the target of a staggering number of studies in order to understand complex neural functions. The corpus striatum is a brain area especially rich in neurotransmitters where cholinergic neurons are supposed to play an associative role between different neuronal types, and therefore their activity is modulated by multiple neurotransmitter systems [Trends Neurosci. 17 (1994) 228; Trends Neurosci. 18 (1995) 527] [13,25]. In this regard, superfusion of synaptosomes is a useful in vitro approach to study the neurotransmitter release allowing an unequivocal interpretation of results obtained under accurately specified experimental conditions. Synaptosomes are sealed presynaptic nerve terminals obtained after homogenating brain tissue in iso-osmotic conditions [J. Physiol. 142 (1958) 187] [22]. Synaptosomes have been extensively used to study the mechanism of neurotransmitter release in vitro because they preserve the biochemical, morphological and electrophysiological properties of the synapse [J. Neurocytol. 22 (1993) 735] [42]. The superfusion, strictly a perfusion, allows both the continuous removal of the compounds present in the biophase of the presynaptic proteins and the easy exchange of the medium. We herein describe the method of superfusion of rat striatal synaptosomes to study the [(3)H]ACh release under basal and stimulated conditions. To depolarize the synaptosomal preparation three different strategies were employed: high extracellular concentration of K(+) (15 mM), a K(+) channel-blocker (4-aminopyridine, 1-30 microM), or veratridine (10 microM) which blocks the inactivation of voltage-dependent Na(+) channels.

Differential effect of quinpirole and 7-OH-DPAT on the spontaneous [(3)H]-dopamine efflux from rat striatal synaptosomes.

The effect of quinpirole and 7-OH-DAPT, two D(2)-like agonists, were examined using superfused rat striatal synaptosomes to study the autoregulation of spontaneous [(3)H]-dopamine ([(3)H]-DA) release. Basal [(3)H]-DA efflux was Ca(2+)-dependent by approximately 45% and was inhibited by cadmium 10 microM by 24%. Quinpirole (1 nM to 3 microM) inhibited spontaneous [(3)H]-DA efflux in a concentration-dependent manner (pEC(50) = 7.56 +/- 0.07 and E(max) = 26 +/- 0.09%) and this effect was competitively antagonized by haloperidol (0.3-1 nM) (apparent pA(2) = 9.61 +/- 0.08). In addition, activation of the D(2) DA autoreceptor by quinpirole only modulates the calcium-dependent component of [(3)H]-DA efflux. Low concentrations of a putative-selective D(3) DA agonist, (+/-)-7-OH-DPAT (0.03-0.1 microM), inhibited spontaneous [(3)H]-DA release by 13% (P < 0.05), but higher drug concentrations (> or =1 microM) increased basal [(3)H]-DA efflux in a concentration-dependent, nonsaturable, but reversible manner. Haloperidol (1-10 nM) reversed the (+/-)-7-OH-DPAT-induced inhibition, but not the increase in [(3)H]-DA outflow. The effect of (+/-)-7-OH-DPAT was mimicked by (+)-7-OH-DPAT. However, another putative D(3) DA agonist, PD 128,907 (1 nM to 3 microM), decreased spontaneous tritium efflux (maximal inhibition of 19 +/- 3.06% at 3 microM, P < 0.01). The effect of 7-OH-DPAT 10 microM was independent of the presence of extracellular Ca(2+), since its effect on basal [(3)H]-DA outflow was not significantly modified in a 200 nM free-Ca(2+) medium. In addition, the 7-OH-DPAT-induced enhancement of basal [(3)H]-DA efflux does not involve depolarization of nerve terminals or the reversal of the DA uptake system, as tetrodotoxin (1 microM) and nomifensine (1microM) did not modify the effect of 7-OH-DPAT 10 microM. The present data indicate that activation of D(2) DA autoreceptor subtype by quinpirole inhibits Ca(2+)-dependent spontaneous [(3)H]-DA efflux. 7-OH-DPAT activates the D(2) DA autoreceptor at low concentrations, whereas its action in releasing [(3)H]-DA effect is not receptor-mediated and could involve other mechanisms other than either conventional vesicular exocytosis or the DA uptake system.

Presynaptic modulation of K+-evoked [3H]dopamine release in striatal and frontal cortical synaptosomes of normotensive and spontaneous-hypertensive rats.

Regional differences in presynaptic [3H]dopamine ([3H]DA) release and its modulation by D2 DA-receptors between the frontal cortex and striatum obtained from Wystar-Kyoto (WKY) and spontaneous-hypertensive rats (SHR) have been evaluated using superfused synaptosomes. Synaptosomal tritium content was significantly lower in the frontal cortex than in the striatum in both SHR and WKY (approximately 45% and 48%, respectively), but no differences in tritium content were obtained between strains. However, the 15 mM K+-evoked [3H]DA overflow was lower in the SHR as compared to WKY rats in both brain regions (striatum approximately 23%, frontal cortex approximately 21). Concentration-response curves for quinpirole (1nM-10 microM)-mediated inhibition of 15mM K+-evoked [3H]DA release showed no differences between SHR and WKY. These results suggest that SHR has less ability to release [3H]DA as compared to WKY rats, but SHR did not show differences in the autoregulation of such release in both the frontal cortex and striatum.

Microcomputed tomography of kidneys following chronic bile duct ligation.

BACKGROUND: In hepatic cirrhosis, renal sodium and water retention can occur prior to decreases in renal blood flow (RBF). This may be explained in part by redistribution of the intrarenal microcirculation toward the juxtamedullary nephrons. To appreciate this three-dimensional spatial redistribution better, we examined the intrarenal microcirculatory changes using microcomputed tomography (micro-CT) in rats subjected to chronic bile duct ligation (CBDL). METHODS: Six kidneys from control rats and eight kidneys from rats that had undergone CBDL for 21 days were perfusion fixed in situ at physiological pressure, perfused with silicon-based Microfil containing lead chromate, embedded in plastic, and scanned by micro-CT. The microvasculature in the reconstructed three-dimensional renal images was studied using computerized image-analysis techniques. To determine the physiological condition of the rats, parallel experiments were conducted on six control and six CBDL rats to measure mean arterial pressure (MAP), RBF, glomerular filtration rate (GFR), urine flow (UF) rate, and sodium excretion by conventional methods. RESULTS: The percentage of vasculature in the renal cortex from CBDL rats was significantly decreased (10.8 +/- 0.4% vs. 16.8 +/- 2.7% control values). However, the vascular volume fractions of the medullary tissues were not significantly altered. There were no significant differences in the number of glomeruli between groups (36,430 +/- 1908 CBDLs, 36,609 +/- 3167 controls). The CBDL rats had a similar GFR than the controls but a reduced MAP, RBF, UF, and sodium excretion. CONCLUSIONS: The results indicate that after CBDL, there is a selective decrease in cortical vascular filling, which may contribute to the salt and water retention that accompanies cirrhosis.

Three-dimensional microcomputed tomography of renal vasculature in rats.

Current microscopic methods to view renal microvasculature reveal only a very limited portion of the total renal volume. Identification of connectivity for postglomerular vessels in the cortex and the medulla during functional states related to changes in sodium excretion will help better to understand the coupling of renal vasculature to tubular function. The purpose of this study was to investigate the possibility of visualizing the continuity of pre- and postglomerular vasculature using three-dimensional micro-computed tomography (micro-CT). Kidneys from normal rats were perfusion fixed in situ at physiological pressure, filled with latex microfil containing lead chromate, and embedded in plastic. The micro-CT scans of the intact kidneys were carried out on a rotating stage illuminated either by a synchrotron x-ray source or a conventional x-ray spectroscopy tube. Images were reconstructed by a filtered backprojection algorithm and volume-rendering techniques were utilized to display the vasculature. The reconstructed images clearly showed the large distribution vessels and the venous drainage of the kidneys, while pre- and postglomerular vessels and their vascular connections throughout the kidney were displayed in great detail. Efferent arterioles showed the characteristics of their peritubular capillary beds in the cortical and medullary regions. The vascular volume of the cortex was 27%, the outer stripe of the outer medulla 18%, the inner stripe of the outer medulla 30%, and the inner medulla 18%. In conclusion, micro-CT is a promising method to evaluate renal vascular architecture relative to physiological and pathological alterations.

D2 dopamine receptors and modulation of spontaneous acetylcholine (ACh) release from rat striatal synaptosomes.

1. The effect of two D3/2 dopamine receptor agonists, LY-171555 (quinpirole) and 7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) on spontaneous [3H]-acetylcholine ([3H]-ACh) release were investigated in rat striatal synaptosomes. 2. Quinpirole and 7-OH-DPAT inhibited in a concentration-dependent manner the basal efflux of [3H]-ACh with similar Emax (maximal inhibitory effect) values (29.95 +/- 2.91% and 33.19 +/- 1.21%, respectively). Significant differences were obtained between the pEC50 (-log of molar concentration) of quinpirole (7.87 +/- 0.12) and 7-OH-DPAT (7.21 +/- 0.17; P < 0.01). 3. Different concentrations (0.3-10 nM) of haloperidol (D2/3 dopamine receptor antagonist) shifted to the right the concentration-response curves elicited by quinpirole and 7-OH-DPAT, without modifications in the Emax. 4. Slopes of a Schild plot obtained with haloperidol in the presence of quinpirole and 7-OH-DPAT were not significantly different from unity (0.85 +/- 0.05 and 1.17 +/- 0.11, respectively) and consequently haloperidol interacted with a homogeneous receptor population. The pKB values of haloperidol obtained from Schild regression were 9.96 +/- 0.15 (in presence of quinpirole) and 9.90 +/- 0.09 (in presence of 7-OH-DPAT). 5. Specific binding of [3H]-YM-09151-2 to membranes of striatal synaptosomes and cells expressing D2 and D3 dopamine receptors was inhibited by haloperidol. Analysis of competition curves revealed the existence of a single population of receptors. There were no differences between the estimated pKi (-log of molar concentration) values for synaptosomes (8.96 +/- 0.02) and cells expressing D2 receptors (8.81 +/- 0.05), but the pKi value from cells expressing D3 dopamine receptors differed significantly (8.48 +/- 0.06; P < 0.01). 6. In conclusion, the data obtained in the present study indicate that quinpirole and 7-OH-DPAT, two D3/2 dopamine receptor agonists, inhibit the spontaneous [3H]-ACh efflux and this effect is competitively antagonized by haloperidol and probably mediated through dopamine D2 receptors.

Effect of 1-aminocyclopropanecarboxylic acid on N-methyl-D-aspartate-stimulated [3H]-noradrenaline release in rat hippocampal synaptosomes.

1. The effect of 1-aminocyclopropanecarboxylic acid (ACPC), a partial agonist at the glycine site of the N-methyl-D-aspartate (NMDA) receptor complex that exhibits neuroprotective, anxiolytic and antidepressant-like actions, was investigated in a functional assay for presynaptic NMDA receptors. 2. NMDA (100 microM) produced a 36% increase of tritium efflux above basal efflux in rat hippocampal synaptosomes preincubated with [3H]-noradrenaline ([3H]-NA), reflecting a release of tritiated noradrenaline. This effect was prevented by 10 microM 7-chlorokynurenic acid, an antagonist of the glycine site of the NMDA receptor. 3. Glycine enhanced the effect of NMDA with Emax and EC50 values of 84 +/- 11% and 1.82 +/- 0.04 microM, respectively. ACPC potentiated the effect of NMDA on tritium overflow with a lower EC50 (43 +/- 6 nM) and a lower maximal effect (Emax = 40 +/- 9%) than glycine. Furthermore, ACPC (0.1 microM) shifted the EC50 of glycine from 1.82 microM to > or = 3 mM. 4. These results show that ACPC can reduce the potentiation by glycine of NMDA-evoked [3H]-NA release and hence, may act as an antagonist at the glycine site of presynaptic hippocampal NMDA receptors when the concentration of glycine is high.

El riñon en la hipertensión arterial esencial / The kidney in te essential arterial hypertensión

No está bien dilucidada la posibilidad de que una hipertensión arterial esencial (HAE) leve-moderada sea capaz de llevar a un paciente a una insuficiencia renal crónica terminal (IRCT). Se planificó este trabajo con el objeto de estudiar los cambios que se producen en el riñon de pacientes con hipertensión esencial leve-moderada (n=148) reflejados sobre la depuración de creatinina (método de Jaffé) y de la excreción urinaria de albúmina (microalbuminuria), método del ácido sulfosalicílico), al compararlos con un grupo de sujetos normotensos (N=192). Los hipertensos presentaron una correlación inversa y significativa entre tensión arterial sistólica (TAS) (p<0,0001), tensión arterial diastólica (TAD), con la depuración de creatinina. Así mismo se encontró una correlación directa y muy significativa entre TAS (p<0,0001) y TAD (p<0,0001), con la excreción urinaria de albúmina. La TAS influyó más efectivamente sobre ambos parámetros. Esta acción se manifesto precozmente en los jóvenes (15-30 años) y se acentúa en los ancianos. La tensión arterial elevada se va a sumar a la edad para que la decline la función renal y se incremente la microalbuminuria, aunque moderadamente. El 38 por ciento de los hipertensos estudiados (15-60 años) presentaron microalbuminuria. En los mayores de 60 años, esta cifra se incrementa a un 55 por ciento. En el grupo de hipertensos entre los 30-60 años, se encontraron cifras más elevadas de aldosterona plasmática (p<0,0001) y una correlación significativa entre AP y microalbuminuria (p<0,01). La HAE leve-moderada, se suma al factor edad para alterar la función renal, aunque de manera moderada. Pensamos que esta alteración sí puede llevar al paciente a una IRCT, pero en un porcentaje bajo (15-60 años) presentaron microalbuminuria, cifra que aumentó a un 55 por ciento, por encima de 60 años. Estos son los pacientes que necesitan un control más estricto de hipertensión. En el grupo de hipertensión comprendida entre 30-60 años; sugerimos que la angiotensina II y la aldosterona deben jugar un papel contribuidor importante en la patogenia de la microalbuminuria

El peptido natriuretico auricular y el sistema renina-aldosterona en el anciano normal y en el hipertenso: respuesta a los suplementos del calcio / The natruretia atrial peptide and the renin-aldosterone system in hormal and hypertensive elder, response to calcium

La concentracion plasmatica del peptido natriuretico auricular se encuentra elevada en los ancianos y si son hipertensos, sus valores son mucho mas altos. Con el obejto de estudiar el peptido natriuretico auricular y la respuesta del sistema angiotensina aldosterona, se le administro un suplemento de calcio oral a un grupo de ancianos hipertensos y a otro grupo de normotensos, que nos sirvio de control. Se seleccionaron 22 ancianos hipertensos (2 hombres y 20 mujeres), con una edad de 75 +/- años y 10 ancianos normotensos (2 hombres y 8 mujeres) con igual promedio de edad. Se le practicaron tomas tensionales con esfignomanometro de Hg en 3 posiciones (de cubito, sentado y de pie). Por el metodo de radioinmunoensayo se les dosificaron el peptido natriuretico auricular, de actividad de la renian plasmatica, la aldosterona plasmatica por absorcion atomica se le determino el calcio serico total, antes y despues de recibir 1.5 g/dia de CaCO3, por un periodo de 4 semanas. En los hipertensos se obtuvieron los siguientes resultados: el peptido natriuretico auricular descendio de manera imporatante (P<0.001), en igual forma lo hizo la aldosterona (P<0.001), por el contrario la reina (P<0.001) y el Calcio (P<0.001) aumentaron sus valores. Igualmente se consiguieron las correlaciones inversas entre renina/peptido y entre peptido/calcio, pero no se observo esta relacion entre aldosterona/peptido. En los acnianos normotensos, se obtuvo un descenso del peptido (P<,05) y un incremento del calcio serico total (P<0,05). En los hipertensos descendieron sus cifras tensionales sistolica (P<0.001) y las distolicas (P<0,05). Estos resultados ponene en evidencia las relaciones tan estrecha que existen entre la tension arterial (especialmente la sistolica, peptido, renina, aldosterona, calcio serico en ancianos hipertensos y menos significativos en los normotensos. En conclusion la administracion de calcio oral a ancianos, especialmente hipertensos, determino en ellos una serie de cambios en los grupos hormonales que manejan la homeostasis agua-sodio. Esta accion se ejerce probablemente de manera indirecta, yaque al actuar como hipotensor, se van a corregir lasalteraciones antes mencionadas en los dos grupos hormonales que intervienen en este equilibrio.

Differential contribution of L- and N-type calcium channels on rat hippocampal acetylcholine release.

Bay K 8644, nimodipine and omega-conotoxin GVIA (omega-CgTx) were used to study the different contribution of voltage-sensitive calcium channels (VSCC) to [3H]acetylcholine ([[3H]ACh) release in rat hippocampal synaptosomes. In our experimental conditions, the percentage of calcium-dependent ACh release was approximately 80%. Nimodipine (0.01-10 microM) and Bay 8644 (0.01-10 microM) were not able to modify the [3H]ACh release under stimulating conditions (15 mM K+). Nevertheless, when K+ concentration was reduced to 8 mM, a significant increase in [3H]ACh release was observed at 1 and 10 microM of Bay K 8644. Nimodipine (0.01-10 microM) failed to reverse the effect of Bay K 8644 on [3H]ACh release. Finally, omega-CgTx (0.001-1 microM) caused a concentration-dependent reduction of [3H]ACh release in K+ (15 mM)-stimulating conditions. These results suggest that the N-type VSCC probably play a predominant role in regulating the [3H]ACh release in synaptosomes from rat hippocampus.

El péptido natriurético auricular y el sistema renina-aldosterona en el anciano normal y en el hipertenso: respuesta a los suplementos del calcio / Atrial natriuretic peptide and the system renin-angiotensin in the normal age and hypertense: response to calcium supplementation

La concentración plasmática del péctido natriurético auricular se encuentra elevada en los ancianos y si son hipertensos, sus valores son mucho mas altos. Con el objeto de estudiar el péptido natriurético auricular y la respuesta del sistema angiotensina aldosterona, se le administró un suplemento de calcio oral a un grupo de ancianos hipertensos y a otro grupo de normotensos, que nos sirvió de control. Se seleccionaron 22 ancianos hipertensos (2 hombres y 20 mujeres) con una edad de 75 ñ 7 años y 10 ancianos normotensos (2 hombres y 8 mujeres) con igual promedio de edad. Se le practicaron tomas tensionales con esfigmomanómetro de Hg en tres posiciones (decúbito, sentado y de pie). Por el método de radioinmunoensayo se les dosificaron el péptido natriurético auricular, la actividad de la renina plasmática, la aldosterona plasmática. Por absorción atómica se determinó el calcio sérico total, antes y después de recibir 1,5 g/día de Ca CO3 por un período de 4 semanas. En los hipertensos se obtuvieron los siguientes resultados: el péptido natriurético auricular descendió de manera importante (p<0,001), en igual forma lo hizo la aldosterona (p<0,001), por el contrario la renina (p<0,001) y el calcio (p<0,001), aumentaron sus valores. Igualmente se consiguieron las correlaciones inversas entre renina/péptido y entre péptido/calcio, pero no se observó esta relación entre aldosterona/péptido. En los ancianos normotensos, se obtuvo un descenso del péptido (p<0,05) y un incremento del calcio sérico total (p<0,05). En los hipertensos descendieron sus cifras tensionales sistólica (p<0,001) y las distólicas (p<0,05). Estos resultados ponen en evidencia las relaciones tan estrechas que existen entre la tensión arterial (especialmente la sistólica), péptido , renina, aldosterona, calcio sérico en ancianos hipertensos y menos significativos en los normotensos. En conclusión: la administración de calcio oral a ancianos, especialmente hipertensos, determinó en ellos una serie de cambios en los grupos hormonales que manejan la homeostasis agua-sodio. Esta acción se ejerce probablemente de manera indirecta, ya que al actuar como hipotensor, se van a corregir las alteraciones antes mencionadas en los dos grupos hormonales que intervienen en este equilibrio