[-174 G/C polymorphism of interleukin 6 gene in women with type 1 diabetes]. / Polimorfismo -174 G/C del gen promotor de interleuquina 6 en mujeres con diabetes mellitus tipo 1.

BACKGROUND: A polymorphism located in the promoter region (-174 G/C) of interleukin 6 (IL-6) has been linked to early onset of type 1 diabetes (T1D) and increased body mass index (BMI). AIM: To evaluate the possible association of this -IL-6 gene 174 GIC polymorphism with T1D, BMI and metabolic control in T1D patients in a case-control study. PATIENTS AND METHODS: -174 G I C polymorphisms were analyzed by polymerase chain reaction and restriction fragment length polymorphism in 145 women with T1D and 103 healthy controls. BMI and BMI-Z-scores were tabulated and metabolic control was recorded. RESULTS: There was a higher frequency for the C allele in T1D patients compared with the control group (21% versus 14.1%, p = 0.047). No significant differences in genotype frequencies for the -174 GIC polymorphism of IL-6 gene between patients with T1D and controls, were observed. There were no significant associations with T1D and BMI. CONCLUSIONS: A higher frequency of C allele in women with T1D was the only finding in this series, suggesting that the polymorphic variant is not related to weight gain in these patients.

Polimorfismo -174 G/C del gen promotor de interleuquina 6 en mujeres con diabetes mellitus tipo 1 / -174 G/C polymorphism of interleukin 6 gene in women with type 1 diabetes

Background: A polymorphism located in the promoter region (-174 G I C) of interleukin 6 (IL-6) has been linked to early onset of type 1 diabetes (T1D) and increased body mass index (BMI). Aim: To evaluate the possible association of this -IL-6 gene 174 GIC polymorphism with T1D, BMI and metabolic control in T1D patients in a case-control study. Patients and Methods:-174 G I C polymorphisms were analyzed by polymerase chain reaction and restriction fragment length polymorphism in 145 women with T1D and 103 healthy controls. BMI and BMI-Z-scores were tabulated and metabolic control was recorded. Results: There was a higher frequency for the C allele in T1D patients compared with the control group (21 percent versus 14.1 percent, p = 0.047). No significant differences in genotype frequencies for the -174 GIC polymorphism of IL-6 gene between patients with T1D and controls, were observed. There were no significant associations with T1D and BMI. Conclusions: A higher frequency of C allele in women with T1D was the only finding in this series, suggesting that the polymorphic variant is not related to weight gain in these patients.

Diabetes mellitus tipo 2 e intolerancia a la glucosa en niños y adolescentes con obesidad: ¿una epidemia moderna? / Frequency of diabetes mellitus and glucose intolerance among obese children and adolescents

Background: The prevalence obesity, type 2 diabetes (DM2) and glucose intolerance among children is increasing worldwide. Aim: To assess the frequency of DM2 and GI among severely obese children and adolescents. Patients and methods: Cross sectional study of 69 children and adolescents aged 12 +/- 3 years with a mean body mass index (BMI) z score of 2.9 +/- 0.6. An oral glucose tolerance test (OGTT) was performed, measuring fasting and 120 minutes blood glucose and insulin. According to these results two patients had diabetes mellitus and 4 had glucose intolerance. Previously studied patients, five with diabetes mellitus and two with glucose intolerance were incorporated to the present study. These 13 participants were compared with the remaining 63 children without abnormalities in glucose metabolism, considered as controls. Results: Body mass index among children with glucose intolerance, diabetes mellitus and controls was 33.8 +/- 6.4, 26.7 +/- 5.1 and 29.4 +/- 4.5 kg/m2, respectively, p = 0.03. Basal and 120 min insulin levels were also significantly higher among children with glucose intolerance compared with diabetics and controls. Homeostasis model assessment for insulin resistance was significantly lower in controls than in children with diabetes or glucose intolerance. Conclusions: Eight percent of this group of obese children and adolescents had DM2 or glucose intolerance. Oral glucose tolerance test should be included in the routine assessment of obese children to diagnose abnormalities of glucose metabolism.

Relación entre el polimorfismo -34 Bp de la región promotora del gen CYP17 con el perfil hormonal y metabólico en mujeres con diabetes mellitus tipo 1 / Relationship of -34 Bp polymorphism in the promoter of Cyp17 gene with hormonal and metabolic profile in women with type 1 diabetes mellitus

The P450c17a enzyme has a central role in ovarian hyperandrogenism, which is a characteristic of polycystic ovary syndrome (PCOS). Several studies have suggested a possible role for the CYP17 gene, which codes for the enzyme P450c17a and the -34bp T-C polymorphism in the development of hyperandrogenism. The presence of the cytosine, know as A2 allele, has been associated with hyperandrogenism in patients with PCOS. Objective: To evaluate the frequency and association of the -34bp polymorphism in the CYP17 gene and determine its association with hormonal and metabolic characteristics in women with DM1. Patients and Methods: The CYP17 polymorphism was studied in 72 DM1 and 71 control women by PCR and RFLP analysis. The CYP17 genetic dosage was compared with the antropometrical characteristics and the serum concentrations of testosterone, androstenedione, DHEAS and 17OH progesterone in women with DM1. Results: Genotype A2/A2 was present in 20.8 percent and 7.1 percent of DM1 and controls, respectively (p = 0,034). Allele A2 was present in 40.3 percent and 27.5 percent of DM1 and healthy women, respectively (p = 0,031). No association between CYP17 genotypes and hormonal or metabolic characteristics was observed. Conclusion: This study shows that the frequency of the A2/A2 genotype was higher in women with DM1 than in the control group. However, no association between the presence of the polymorphism and circulating steroid levels or BMI was observed.

Fifty years of progress in carotid body physiology--invited article.

Research on arterial chemoreceptors, particularly on the carotid body, has been fruitful in the last fifty years, to which this review is addressed. The functional anatomy of the organ appears to be well established. The biophysical bases by which glomus cells transduce chemical changes in the milieu intérieur (hypoxia, hypercapnia, acidosis) into electrical and biochemical changes in glomus cells have received much attention. Physical changes (in temperature, flow and osmolarity) are also detected by the carotid body. Electrical coupling between glomus cells themselves appears as very extensive. Sustentacular cells classically considered as ensheathing glia for glomus cells and nerve endings now appear to behave as stem cells precursors for glomus cells under chronic hypoxic conditions. Many papers have been devoted to transmitters released from glomus cells (acetylcholine, dopamine, ATP) and well as to their effects upon chemosensory nerve activity. Chemosensory neurons have been explored from generation of action potentials at peripheral nerve endings, passing to properties of perikarya at petrosal ganglia and finally at characterization of synaptic transmission at solitary tract nuclei. There is abundant literature on ventilatory and cardiovascular reflexes elicited from arterial chemoreceptors. The transient effects of sudden and brief withdrawal of chemosensory discharges by hyperoxia also provide clues on the role played by carotid bodies in the homeostasis of full organisms.

Evaluación de un programa integral de tratamiento de obesidad y sobrepeso en niños escolares y adolescentes en Santiago de Chile (1999-2006) / Assessment of a multidisciplinary program for the treatment of obesity in children

Background: Medical treatment of obesity requires a multidisciplinary approach including dietary, exercise and behavioral interventions. Aim: To report the results of a multidisciplinary program for the treatment of obesity in children. Patients and Methods: Three hundred twenty four children (155 males), aged between 5 and 18 year, were treated with diet, exercise and behavioral modification, between 1999 and 2006. At baseline and at the end of follow up, weight, height, z score for body mass index (BMI), blood pressure and features of the metabolic syndrome were assessed. Results: z scores for IMC decreased by 0.28 points (95 percent confidence intervals: -0.31 to -0.25). Sixty percent of patients achieved a weight reduction of 5 percent of more of their initial weight. In a multiple linear regression model, weight loss was directly associated with the follow up time and inversely associated with the initial waist circumference. Patients had a reduction of 0.05 z score points of BMI per month (95 percent confidence intervals –0.07 to –0.025; p < 0.001), while adhering to the program. The overall compliance with the three months treatment period was 59 percent. Conclusions: In children and teenagers, a multidisciplinary management of obesity achieves a sustained weight loss, that ifs proportional to the lapse of adherence to the program.

Hipertiroidismo y síndrome de Down: caso clínico / Hyperthyroidism and Down syndrome: a present diagnosis

A female patient with Down Syndrome and without cardiac defects. During infancy, she had low weight increment secondary to repeated hospital admissions due to obstructive respiratory tract episodes. In addition, she attends regularly to the gastroenterology clinic due to intermittent diarrhea. At the age of 9.4 years-old, she presented liquid stools 5-6 times/day, associated to a decrease of 7 kg in 5 months and marked hyperactivity. She is admitted with tachycardia, arterial hypertension and high liver enzymes (SGOT = 63 U/1 and SGPT = 97U/1). The ECG showed sinus tachycardia. She is discharged without etiological diagnosis. In the mean time, annual thyroid function requested for endocrinology control showed TSH < 0,1 uUI/ml, T3 = 482 ng/dl and total T4 = 15,4 ug/dl, evidencing clear hyperthyroidism and beginning therapy with propylthiouracil 10 mg/kg/day and propanolol 1,3 mg/kg/day. After 3 weeks, the patient showed less hyperactivity, normal stools, normal sleep-awake cycle and recovered weight. By 6 weeks, thyroid hormones and transaminases were within normal ranges.

Objetivo: Describir una asociación poco frecuente de Síndrome de Down con Hipertiroidismo. Caso Clínico: Paciente de sexo femenino, portadora de síndrome de Down, sin antecedentes de cardiopatía congénita. Evolucionó con mal incremento ponderal en el período de lactante, hospitalizaciones repetidas por cuadros respiratorios obstructivos. En control en gastroenterología por episodios de diarrea intermitente, y en genética en forma regular. Cuadro actual se inicia a los 9,4 años, caracterizado por deposiciones líquidas 5-6 veces al día, asociado a baja de peso aproximada de 7 kg en 5 meses e hiperactividad. Se hospitalizó para estudio y se pesquisaron cifras tensionales elevadas y taquicardia. En perfil bioquímico aparece SGOT 63 U/1 y SGTP 97 U/1. Electrocardiograma informa taquicardia sinusal. Alta sin etiología clara, se solicita función tiroidea: TSH < 0,1 uUI/ml, T3 482 ng/dl, T4 total 15,4 ug/dl realizándose diagnóstico de hipertiroidismo. Inició terapia con propiltiouracilo 10 mg/kg/día y propanolol 1,3 mg/kg/día. A las 3 semanas de iniciado el tratamiento, la paciente presenta menor hiperactividad, deposiciones normales, regulación de la hiperactividad y ciclo sueño-vigilia, recuperando peso. A las 6 semanas, los niveles de T3, T4 y transaminasas eran normales. El hipertiroidismo se observa con mucha menor frecuencia que el hipotiroidismo en niños y adultos con síndrome de Down. En series numerosas de pacientes con trisomía 21, se describen en general un bajo porcentaje de casos de hipertiroidismo, dentro de los cuales se incluyen la enfermedad de Graves y la Hashitoxicosis.

Panhipopituitarismo y diabetes insípida secundarios a hipofisitis linfocitaria en una paciente con trisomia 12p / Panhypopituitarism and diabetes insipidus secondary to a lymphocytic hypophysitis in one patient with trisomy 12p

Lymphocytic hypophysitis (LH) is an uncommon inflammatory disease of the hypophysis. It's female to male ratio of appearance is 9:1. Pregnant women are more affected during the third trimester of pregnancy or postpartum. Clinical and radiological presentation can simulate a hypophyseal adenoma. We report a nonpregnant 13 years old adolescent, with a trisomy 12p, with panhypopituitarism, diabetes insipidus and a selar tumor. It was necessary to differentiate between a germinoma and a LH. The latter was confirmed with the hypophyseal biopsy.

Diabetes Mellitus tipo 1 (DM1) en niños menores de 5 años: Características al debut vs otros grupos etarios en Chile / Type I diabetes mellitus in Chilean children under 5 years-old: Onset characteristics in contrast with other age groups

Introducción: En los últimos años, se ha visto un aumento en la incidencia de DM1 en niños. Objetivo: Determinar frecuencia y características clínicas y de laboratorio al debut de DM1 en niños chilenos menores de 5 años, comparado con los de mayor edad. Pacientes y Métodos: Se estudiaron los datos clínicos y de laboratorio de pacientes que debutaron entre 1998-2003 en cuatro centros de Santiago. Se clasificaron en 3 grupos etarios (G): 0-4 (GI), 5-9 (GII) y 10-14 años (GIII) y se compararon según los parámetros descritos. Resultados: Un 19,7 por ciento de los pacientes eran menores de 5 años; GI (n = 27), seguido de aquéllos pertenecientes a GII (43,8 por ciento; n = 60) y GIII (36,5 por ciento; n = 50). El periodo de síntomas previo al diagnóstico fue más corto en GI; 18,4 ± 23,7 vs 26,4 ± 27,4 y 40,1 ± 60 días (p < 0,0001) y su nivel de HbA1c fue más baja; 10,1 ± 1,7 vs 11,8 ± 3,4 por ciento en GII (p < 0,0001) y 12,4 ± 2,6 por ciento en GIII (p = 0,028), respectivamente. No hubo diferencias en la glicemia inicial entre los grupos. La acidosis metabólica fue mayor en GI; pH 7,14 ± 0,1 vs 7,19 ± 0,2 (GII) y 7,26 ± 0,1 (GIII) (p < 0,0001) y presentaron más infecciones concomitantes (33 por ciento, 20 y 28 por ciento respectivamente; p > 0,05). Conclusiones: Un porcentaje importante de las DM1 se inicia en niños < 5 años. Este grupo presenta un cuadro más grave, con mayor acidosis, menores niveles de HbA1c y periodo previo de síntomas, por lo que debe existir alerta para el diagnóstico en este grupo etario.

Background: During the last years, an increase in the incidence of DM1 in infants has been observed. Objective: to study the number of children younger than 5 years-old diagnosed with DM1 and compare clinical and laboratory features with older children at DM1 onset. Method: Study of the clinical and laboratory characteristics in subjects diagnosed with DM1 from 1998 to 2003 in Santiago. Patients were classified according to age in 3 groups: 0-4 (GI), 5-9 (GII) and 10-14 years-old (GIII). Results: 19,7 percent cases were younger than 5 years-old (GI n = 27), GII (43,8 percent n = 60) and GIII (36,5 percent n = 50). A shorter duration of symptoms was observed in GI (18,4 ± 23,7 vs 26,4 ± 27,4) (p < 0,0001) and HbA1c levels were lower in GII (10,1 ± 1,7 vs 11,8 ± 3,4 percent) (p < 0,0001) and in GIII (12,4 ± 2,6 percent) (p = 0,028). Glucose levels were similar among groups (p>0,05) and metabolic acidosis was more severe in GI (pH 7,14 ± 0,1 vs 7,19 ± 0,2 in GII and 7,26 ± 0,1 in GIII) (p < 0,0001). A concomitant infectious disease was observed in GI (33 percent), GII (20 percent) and GIII (28 percent) (p > 0,05). Conclusions: An important percentage of DM1 in children presents in subjects younger than 5 years-old. This group showed acute and severe clinical presentation with longer duration of symptoms, severe acidosis and lower HbA1c levels. It is necessary to evaluate carefully in order to suspect the diagnosis in this group.

Effects of prolonged hypobaric hypoxia on carotid nerve endings and glomus cells. Changes in intercellular coupling.

Carotid bodies were removed from anesthetized rats kept under normobaric (640 Torr) and hypobaric conditions (380 Torr for 2-3 weeks). Slices (100-150 microm) of the organ were viewed under an inverted microscope for simultaneous stimulation and recording of coupled glomus cells and carotid nerve endings. The latter were identified by their more negative Em, high input resistance (Ro) and time-dependent rectification in response to negative current pulses. Also, when nerve endings had an Em more negative than -40 mV showed spontaneous activity in the form of mini-receptor potentials (mrps). Glomus cells had less negative Em and lower Ro. Prolonged hypobaric hypoxia did not change the Em of nerve endings and glomus cells. However, in both structures, Ro increased. Also, the mrps became smaller and occurred less frequently. Intercellular coupling was recognized when currents applied to one cell spread to adjoining ones. In the case of glomus cells (GC/GC coupling), it was mostly resistive and bidirectional. Coupling between nerve endings and glomus cells was more complex, When a glomus cell was stimulated, current spread to the nerve ending (GC/NE coupling) was similar in magnitude (2-3%) to coupling between GCs. However, when NE was stimulated current spread to GC (NE/GC coupling) was minimal (less than 0.1%) and transient (capacitive). Nerve endings were also bidirectionally and capacitively coupled (NE/NE coupling) with a median of 2,8%. Intracellularly injected Lucifer Yellow or Alexa 488 diffused to neighboring structures. Prolonged hypobaric hypoxia significantly tightened coupling modes GC/NE, NE/GC, and NE/NE but reduced GC/GC coupling. Tighter coupling was accompanied by lower coupling resistance, and the opposite occurred when intercellular coupling decreased. Increased GC/NE and reduced GC/GC coupling during hypobaric hypoxia may be partly responsible for the increased reactivity of these receptors under this condition.

Análogos de insulina: en búsqueda del reemplazo fisiológico / Insulin analogues: searching for a physiological replacement

Insulin analogues, developed by molecular engineering, have structural changes in the A and B insulin chains. These modifications change their action profile, rendering insulin replacement closer to physiology. Rapid acting analogues like lispro, aspart and glulisine, are absorbed rapidly from the subcutaneous tissue to the circulation. In addition, two long acting insulin analogues have been developed: glargine and detemir. The combination of a long acting insulin, to maintain baseline levels, and multiple daily doses of a rapid acting analogue are the mainstay of basal-bolus therapy. Multiples studies have compared human insulin (NPH and regular) with insulin analogues in patients with type 1 or 2 diabetes mellitus, showing an improvement in the metabolic control, fewer hypoglycemic events and better quality of life. In summary, insulin analogues offer new therapeutic options and allow an individualized intensive treatment.

Prevalencia de sobrepeso y obesidad en niños que se controlan en pediatría ambulatoria en Clínica Las Condes / Prevalence of overweight (OW) and obesity (O) in children attending the paediatric unit of the Clínica Las Condes

La obesidad infantil ha aumentado en Chile y con ella sus riesgos a largo plazo. Objetivo: Determinar la prevalencia de sobrepeso (SP) y obesidad (O) en niños controlados en un centro privado en Chile (Clínica Las Condes = CLC). Pacientes y Métodos: Estudio prospectivo en un año de 1.310 niños entre 2 y 18 años (51,6 por ciento hombres) de 7,19 ± 4,02 años de edad promedio. Se consignó edad, sexo, antropometría, y se calculó Índice de Masa Corporal (IMC, kg/m2) absoluto y percentil (p) y el porcentaje peso/talla ( por ciento P/T). Resultados: Los pacientes se distribuyeron en 3 grupos etarios: 45,7 por ciento entre 2-5, 29,5 por ciento entre 6-10 y 24,8 por ciento >10 años. Un 66,8 por ciento estaba eutrófico (IMC p10-85), SP 13,9 por ciento (IMC p85-95), O 12 por ciento (IMC > p95) y bajo peso (BP) 7,3 por ciento (IMC < p10), sin diferencias según sexo ni grupo etario. Conclusiones: La prevalencia de BP, SP y O en CLC es similar a la observada en niveles socioeconómicos medio-bajos chilenos. La mayor proporción entre 6-10 años hace indispensable su prevención desde la etapa de lactante.

Calcium channels of cultured rat glomus cells in normoxia and acute hypoxia.

Glomus cells harvested from Wistar rat carotid bodies were cultured for 4 to 7 days. Inward calcium currents elicited by voltage ramps (0.24 V/s) or pulses were recorded during voltage-clamping in the whole-cell and perforated patch configurations. Currents were enhanced by an excess of [Ca(2+)](o), barium and BayK 8644, and depressed or eliminated by cobalt or nifedipine. Single calcium channels were studied by patch-clamping in the cell-attached configuration with voltage clamp pulses ranging from 0.5 to 50 s. Channel conductances (g) decreased and open times (OT) increased as clamp pulses increased in duration. For comparisons, conductances and OTs obtained with short (0.5-1 s) and long (6-12 s) pulses were grouped as SVH and LVH, respectively. SVH conductances were higher and OTs shorter when compared to LVH. BayK 8644 increased conductances and OT during SVH but this agonist decreased g during LVH. Nifedipine either eliminated channel activity, had no effects or depressed g and OT. Hypoxia (pO(2) 30 Torr) induced by 100% N(2) significantly increased calcium currents in normal bathing solutions and during exposure to 110 mM BaCl(2) in whole-cell and perforated patch recordings. Sodium dithionite (Na(2)S(2)O(4)), lowering pO(2) to 10 Torr, also increased the amplitude of calcium currents, but shifted to more positive voltages the onset and trough (maximum) of calcium currents. N(2)-induced hypoxia increased g and reduced OT during SVH but had opposite effects with longer pulses: conductance decreased and open times increased. N(2)-induced hypoxia increased the numbers of active channels (from 1 to 35) over a mean normoxic level of 47 per cell. It is suggested that increased calcium currents accompany calcium inflow in glomus cells, but calcium influx may not depend exclusively on this mechanism.

Effects of hypoxia and putative transmitters on [Ca2+]i of rat glomus cells.

Dissociated rat glomus cells were loaded with Fura-2 AM to study the effects of hypoxia, and carotid body transmitters on intracellular calcium, [Ca2+]i. The mean control [Ca2+]i was 55 nM in isolated cells and 67 nM in clusters. The following procedures changed [Ca2+]i:0[Ca2+]o+EGTA reduced [Ca2+]i by about 50%, suggesting that the remaining calcium originated from intracellular organelles. [Ca2+]i increased when [Ca2+]o was doubled. Hypoxia by sodium dithionite (Na2S2O4) induced large [Ca2+]i increases in clustered and isolated cells. Smaller rises occurred with 100% N2 hypoxia. The augmented [Ca2+]i, induced by Na2S2O4, was reduced (not eliminated) in 0[Ca2+]o+EGTA, suggesting that some calcium was intracellularly released. Nifedipine depressed (did not block) the Na2S2O4-induced calcium increase, implying some inflow via other (N, T or P/Q) voltage-dependent or voltage-independent calcium channels.Cholinergic agents (ACh, nicotine, muscarine, bethanechol and pilocarpine) increased [Ca2+]i. The ACh effect was produced exclusively by calcium inflow since it was eliminated in 0[Ca2+]o+EGTA. Cholinergic effects were depressed (not obliterated) by D-tubocurarine (D-TC), hexamethonium (C6) and atropine.ACh, nicotine and pilocarpine potentiated the excitatory effect of Na2S2O4 on [Ca2+]i. Bethanechol depressed this excitation whereas muscarine had inconsistent effects. Atropine and C6 depressed [Ca2+]i increases elicited by Na2S2O4 but the effects of D-TC were variable. Dopamine (DA) had variable effects. It increased [Ca2+]i in 75% of cases, and reduced the Na2S2O4 -induced calcium increase.Thus, calcium increases during Na2S2O4 occur by direct effects on the glomus cells and feedback action through released ACh and DA.

Behavior of junction channels between rat glomus cells during normoxia and hypoxia.

The activity of gap junction channels between cultured and clustered carotid body glomus cells of the rat was studied with dual voltage clamping during normoxia (PO(2) 300 Torr) and hypoxia induced by sodium dithionite (Na(2)S(2)O(4)) or 100% N(2). Na(2)S(2)O(4) reduced the saline PO(2) to approximately 10 Torr, whereas 100% N(2) reduced ambient O(2) to approximately 60 Torr. The following observations were made. 1) In normoxia, the intercellular macroconductance (G(j) = 3.0 +/- 1.01 ns, mean +/- SE) was changed unevenly (increased and decreased) under hypoxic conditions by either agent, although N(2) produced the largest changes. 2) The intercellular microconductances of the channels (g(j) = 104.44 +/- 10.16 pS under normoxic conditions) significantly decreased in 100% N(2) but showed depressions and enhancements in Na(2)S(2)O(4). 3) The conductance of single-junction channels (SChs), calculated as g(j) variance/mean g(j), yielded a mean of approximately 17.6 pS. Larger values were obtained with manual measurements of the data (approximately 34 pS). Hypoxic hypoxia (induced by 100% N(2)) significantly depressed the conductance of SChs when calculated from digitized records or from manual measurements. Hypoxia induced by Na(2)S(2)O(4) did not significantly change junctional conductance. 4) The number of intercellular channels, calculated as g(j)/SCh g(j), had a mean of approximately 452 (range 1 to 2,471). During N(2)-induced hypoxia, this number significantly decreased to approximately 84 but remained unchanged during Na(2)S(2)O(4) hypoxia. 5) The mean open time of junction channels varied from 4 to 30 ms in different experiments, having an overall mean of mu = 11.33 +/- 0.33 ms. This value was significantly reduced by 100% N(2) but was not changed by Na(2)S(2)O(4). 6) Intracellular calcium ([Ca(2+)](i)), 46.2 +/- 4.84 nM under normoxia, significantly increased to 77.32 +/- 11.27 nM with Na(2)S(2)O(4) and to 66.39 +/- 11.64 nM with 100% N(2). It is concluded that 100% N(2) uncouples glomus cells by significantly reducing intercellular macro- and microconductances. Hypoxia induced by Na(2)S(2)O(4) had variable effects. The coupling effects of hypoxia may depend on, or be aided by, increases in [Ca(2+)](i) and/or intracellular pH changes. However, secreted transmitters and ATP plus the effects of hypoxia on second messengers and other cytoplasmic components may also play an important role in this phenomenon.

Acidic regulation of junction channels between glomus cells in the rat carotid body. Possible role of [Ca(2+)](i).

The purpose of this work was to characterize the gap junctions between cultured glomus cells of the rat carotid body and to assess the effects of acidity and accompanying changes in [Ca(2+)](i) on electric coupling. Dual voltage clamping of coupled glomus cells showed a mean macrojunctional conductance (G(j)) of 1.16 nS+/-0.6 (S.E.), range 0.15-4.86 nS. At normal pH(o) (7.43), a steady transjunctional voltage (DeltaV(j)=100.1+/-10.9 mV) showed multiple junction channel activity with a mean microconductance (g(j)) of 93.98+/-0.6 pS, range 0.3-324.5 pS. Single-channel conductances, calculated as variance/mean g(j), gave a mean value of 16.7+/-0.2 pS, range 5.13-39.38 pS. Manual measurements of single-channel activity showed a mean g(j) of 22.03+/-0.2 pS, range 1.3-160 pS. Computer analysis of the noise spectral density distribution gave a channel mean open time of 12.7+/-1.5 ms, range 6.37-23.42 ms. The number of junction channels, estimated in each experiment from G(j)/single-channel g(j), showed a range of 7 to 258 channels (mean, 107.2). Optical measurements of [Ca(2+)](i) gave a mean value of 80.2+/-4.27 nM at pH(o) of 7.43. Acidification of the medium with lactic acid (1 mM, pH 6.3) induced: 1) Variable changes in G(j) (decreases and increases); 2) A significant decrease in mean g(j) (to 80.36+/-0.34 pS) and in single-channel conductance (g(j)=12.8+/-0.2 pS in computer analyses and 17.23+/-0.2 pS when measured by hand); 3) Variable changes in open times, resulting in a similar mean (12.8+/-1.5 ms) and 4) No change in the number of junction channels. When pH(o) was lowered to 6.3 [Ca(2+)](i) did not change significantly (there were increases and decreases). However, when pH(o) was lowered to 4.4, [Ca(2+)](i) increased significantly to 157.1+/-8.1 nM. It is concluded that saline acidification to pH 6.3 depresses the conductance of junction channels and this effect may be either a direct effect on channel proteins or synergistically enhanced by increases in [Ca(2+)](i). However, there are no studies correlating changes of [Ca(2+)](i) and intercellular coupling in glomus cells. Stronger acidification (pH(o) 4.4), producing much larger changes in [Ca(2+)](i), may enhance this synergism. But, again, there are no studies correlating these effects.

Carotid body gap junctions: secretion of transmitters and possible electric coupling between glomus cells and nerve terminals.

It is proposed that intercellular coupling between glomus cells and carotid nerve terminals form an integral part of the chemoreceptor process. Coupling is possible because gap junctions occur between these elements. At rest, most glomus cells would be coupled. Stimuli uncouple (or reduce coupling) most glomus cells that extrude their contents toward the nerve terminals. However, other glomus cells do not secrete but recharge and intercellular coupling increases. These phenomena would allow for sustained chemoreceptor activity during prolonged stimulation. Coupling between glomus and sustentacular cells may explain why the behavior of glomus cells in the intact carotid body and when clustered in cultures (when their sustentacular envelope is preserved) is different from that of isolated cells where sustentacular cells are destroyed. The presence of electric synapses between glomus cells and nerve terminals may explain the poor performance of synaptic blockers on natural (hypoxia, hypercapnia, acidity) carotid body stimulation.

Short- and long-term regulation of rat carotid body gap junctions by cAMP. Identification of connexin43, a gap junction subunit.

Intact and cultured carotid bodies (CBs) of the rat were used in this study. Applications of membrane-permeant db-cAMP to cultured carotid bodies increased electric coupling between most glomus cells (increasing junctional conductance) probably by opening preformed intercellular channels. This a short-term effect of the nucleotide, increasing gating between glomus cells. When cultures and intact carotid bodies were treated with membrane-permeant 8Br-cAMP for 3 h or more (to increase cytosolic cAMP), there was enhanced gap junction formation and better dye spread between carotid body cells. Connexin43 (CX43) was identified by immunocytochemical methods as forming part of the intercellular channels between carotid body cells, and the expression of Cx43 increased by cAMP. This is a long-term effect, inducing the formation of gap junctions. Thus, cAMP had short and long-term effects on the intercellular junctions of the carotid body. Long-term formation of gap junctions may be important in modulating carotid body functions during stimulation by chronic hypoxia.