Knocking down the diencephalic thyrotropin-releasing hormone precursor gene normalizes obesity-induced hypertension in the rat.

We recently showed that diencephalic TRH may mediate the central leptin-induced pressor effect. Here, to study the role of TRH in obesity-induced hypertension (OIH), we used a model of OIH produced by a high-fat diet (HFD, 45 days) in male Wistar rats. After 4 wk, body weight and systolic arterial blood pressure (SABP) increased in HFD animals. Plasma leptin was correlated with peritoneal adipose tissue. Then, we treated OIH animals with an antisense oligodeoxynucleotide and small interfering (si)RNA against the prepro-TRH. Antisense significantly decreased diencephalic TRH content and SABP at 24 and 48 h posttreatment. Similar effects were observed with siRNA against prepro-TRH but for up to 4 wk. Conversely, vehicle, an inverted antisense sequence and siRNA against green fluorescence protein, produced no changes. SABP decrease seems to be owing to an inhibition of the obesity-enhanced sympathetic outflow but not to an alteration in thyroid status. Using a simple OIH model we demonstrated, for the first time, that central TRH participates in the hypertension induced by body weight gain probably through its well-known action on sympathetic activity. Thus the TRH-leptin interaction may contribute to the strong association between hypertension and obesity.

[3H]Tyramine uptake by rat liver slices.

Rat liver slices were employed as experimental model to characterise the system involved in the transport process which participates in liver tyramine uptake. The uptake of 0.4 micromol l-1of [3H]tyramine by rat liver slices was linear from 5 min up to the end of incubation. At 15 min the uptake was 4.58+/-0.18 pmol mg-1protein. The accumulation of [3H]tyramine was sensitive to temperature (69. 3+/-4.0% inhibition at 0 degrees C, P<0.001), to sodium omission replaced by 150 mmol l-1Tris or 110 mmol l-1Tris+40 mmol l-1choline (27.6+/-6.0%, P<0.01, and 24.6+/-3.8% inhibition, P<0.01, respectively), and the inhibition of Na+-K+-adenosine triphosphatase by 150 micromol l-1ouabain (20.4+/-2.6% decrease, P<0.01). Uptake of [3H]tyramine was cocaine- (10 micromol l-1) and desipramine- (1 micromol l-1) dependent (32.2+/-6.4%, P<0.05, and 31.6+/-4.0% inhibition, P<0.05, respectively). Uptake of [3H]tyramine in rat liver slices was not modified by 30 micromol l-1isoprenaline, 30 micromol l-1corticosterone, 30 micromol l-1normetanephrine and noradrenaline up to 4 micrometers at higher noradrenaline concentrations tyramine transport was diminished (P<0.05). Results achieved by incubation with increasing tyramine concentrations indicate that at the micromolar level hepatic uptake occurs by a combined passive diffusion and transport-mediated mechanism, whereas at greater tyramine concentrations passive transport predominates. These results suggest that both simple diffusion and a transport-mediated mechanism are involved in this uptake from hepatocytes, which presents features similar to those described for type 1 non-neuronal uptake systems.

Atrial natriuretic factor does not affect norepinephrine catabolism in rat hypothalamus and adrenal medulla.

We have previously reported that atrial natriuretic factor (ANF) increases neuronal uptake and endogenous content of norepinephrine (NE) and diminishes neuronal release, synthesis and turn-over of NE in rat hypothalamus and adrenal medulla. The aim of the present work was to study another aspect of NE metabolism and therefore investigate the possible effects of ANF on NE catabolism. The determination of monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT) activity and deaminates metabolites formation were studied in vitro in rat hypothalamus and adrenal medulla slices. Results showed that, in the hypothalamus, 100 nM ANF diminished MAO activity while 10 nM ANF did not modify the enzyme activity. Conversely, 10 and 100 nM ANF reduced MAO activity in adrenal medulla. On the other hand, the atrial factor modified neither COMT activity nor the formation of deaminates metabolites in the hypothalamus and adrenal medulla. Present results as well as previous findings support a putative role for ANF in the modulation of NE metabolism not only in the hypothalamus but also in the adrenal medulla of the rat, affecting the storage, release and uptake of NE but not its catabolism.

Incidentaloma adrenal com elevaçäo de normetanefrinas urinárias: Caso 04/96 (MAM, RG 095.567-2, Santa Casa de Misericórdia de Belo Horizonte, MG) / Incidental adrenal masses with increase of urinary normetanephrine: Case 04/96 (MAM, RG 095.567-2, Santa Casa de Misericórdia de Belo Horizonte, MG)

O avanço tecnológico na obtençäo de imagens em medicina (ultrassonografia, tomografia computadorizada e ressonância nuclear magnética) tem proporcionado uma precisäo de detalhes cada vez maior. Por isso, a incidência de achados de massas acidentais está aumentando na mesma proporçäo, obrigando-nos a deparar com novos desafios diagnósticos e terapêuticos. O incidentaloma da adrenal apresenta-se nesta categoria, constituindo um problema diagnóstico e um dilema terapêutico. O feocromocitoma é um tumor raro, que incide em apenas 0,1 por cento dos indivíduos hipertensos e se carateriza por extrema variabilidade na sua expressäo clínica. Raramente o tumor é clinicamente silencioso, porém, frequentemente, seu diagnóstico é estabelecido somente após remoçäo de um incidentaloma adrenal ou autópsia. Neste relato de caso apresentamos uma paciente assintomática, portadora de feocromocitoma silencioso, com aumento apenas dos níveis de normetanefrinas urinárias, alertando para a importância da investigaçäo funcional destas massas encontradas incidentalmente. Os resultados alterados em apenas um dos metabólitos urinários de catecolaminas (HPLC) confirmam achados prévios, de serem estes os mais sensíveis para investigaçäo dos incidentalomas adrenais na detecçäo de feocromocitomas.

Separación de aminas biogénicas mediante cromatografía líquida de alta resolución / High-performance liquid chromatographic determination of biogenic amines

En este trabajo se han compilado los distintos modos cromatográficos y sistemas de detección utilizados en la cromatografía líquida de alta resolución de aminas biogénicas. Se indican las características generales del intercambio catiónico, fase reversa, fase reversa de pares iónicos y cromatografía de partición con fase reversa de pares iónicos. También se analizan comparativamente la detección UV, detección fluorimétrica usando fluorescencia nativa o bien derivatización pre- y postcolumna y detección electroquímica de gran utilidad para esta extensa familia de compuestos. Se dan ejemplos de aplicación de interés en el campo bioquímico-clínico, con el análisis de ácido homovainillínico, ácido 3,4-dihidroxifenilacético y ácido 5-hidroxiindolacético en líquido cefalorraquídeo, metanefrinas, ácido 3,4-dihidroxifenilacético, catecolaminas, ácidos urinarios y 3-metoxi-4-hidroxifenilglicol en orina, catecolaminas y 3-metoxi-4-hidroxifenilglicol en plasma, catecolaminas, 3-metoxi-4-hidroxifenilglicol y otros neurotransmisores en cerebro de rata. Se discuten, también, los tratamientos previos requeridos especialmente para orina y plasma, así como las condiciones de conservación y su incidencia en los resultados obtenidos (AU)

Separación de aminas biogénicas mediante cromatografía líquida de alta resolución / High-performance liquid chromatographic determination of biogenic amines

En este trabajo se han compilado los distintos modos cromatográficos y sistemas de detección utilizados en la cromatografía líquida de alta resolución de aminas biogénicas. Se indican las características generales del intercambio catiónico, fase reversa, fase reversa de pares iónicos y cromatografía de partición con fase reversa de pares iónicos. También se analizan comparativamente la detección UV, detección fluorimétrica usando fluorescencia nativa o bien derivatización pre- y postcolumna y detección electroquímica de gran utilidad para esta extensa familia de compuestos. Se dan ejemplos de aplicación de interés en el campo bioquímico-clínico, con el análisis de ácido homovainillínico, ácido 3,4-dihidroxifenilacético y ácido 5-hidroxiindolacético en líquido cefalorraquídeo, metanefrinas, ácido 3,4-dihidroxifenilacético, catecolaminas, ácidos urinarios y 3-metoxi-4-hidroxifenilglicol en orina, catecolaminas y 3-metoxi-4-hidroxifenilglicol en plasma, catecolaminas, 3-metoxi-4-hidroxifenilglicol y otros neurotransmisores en cerebro de rata. Se discuten, también, los tratamientos previos requeridos especialmente para orina y plasma, así como las condiciones de conservación y su incidencia en los resultados obtenidos

Baclofen and noradrenergic function in the rat frontal cerebral cortex.

Possible changes in noradrenergic function were investigated in rat frontal cerebral cortex after acute treatment (1, 2 h) with the GABAB agonist, baclofen. A single i.p. injection of d,l-baclofen 10 mg/kg both reduced noradrenaline (NA) biosynthesis in vivo (31%) and the endogenous concentration of normetanephrine (NMN) (32%) and increased NA levels (28%). Increased [3H]NA uptake (15%) and [3H]dihydroxyphenyl-ethyleneglycol ([3H]DOPEG formation (39%) were observed in cortex slices ex vivo from baclofen-treated animals. The activity of monoamineoxidase (MAO) was unchanged after baclofen treatment. We suggest that baclofen might interfere in vivo with noradrenergic neurotransmission, reducing NA biosynthesis and release in the rat cerebral cortex.

Accumulation of 3H-(+/-)-noradrenaline by isolated rat liver cells.

Using hepatocytes isolated by collagenase perfusion, we studied the accumulation of 3H-noradrenaline. Cells incubated during 15 min in the presence of 0.4 mumol/l 3H-noradrenaline (without inhibition of noradrenaline metabolism) accumulated 8.32 +/- 1.77 pmol/10(6) cells (n = 3). The accumulation of 3H-noradrenaline in isolated parenchymal liver cells was sensitive to 10 mumol/l cocaine (inhibition 36.6 +/- 7.9%, n = 3) and 1 mumol/l desipramine (inhibition 27.2 +/- 6.9, n = 3). Accumulation of 3H-noradrenaline was temperature and sodium dependent (inhibition 33.2 +/- 9.4%, n = 9, when Na+ was replaced by Tris+) and was influenced by the inhibition of the membrane Na(+)-K(+)-adenosine triphosphatase (Na(+)-K(+)-ATPase) by 150 mumol/l ouabain (34.7 +/- 6.9% inhibition, n = 3). Accumulation of 3H-noradrenaline in the hepatocytes was not affected by the presence of uptake2 inhibitors, normetanephrine (30 mumol/l) and corticosterone (30 mumol/l), but was reduced by 30 mumol/l isoprenaline (76.3 +/- 5.0% inhibition, n = 6). Thus, the system that takes up and accumulates noradrenaline in the isolated rat liver cells possesses some characteristics of both, uptake1 and uptake2 systems and appears to be different from other extraneuronal cocaine-sensitive systems, such as the one reported for pulmonary endothelial cells.

The presynaptic effects of aspirin and prostaglandin E2 in the isolated cat heart.

The presynaptic effects of aspirin and prostaglandin E2 (PGE2) were evaluated in the isolated perfused cat heart preparation. Tissue catecholamine stores were studied by labelling the sympathetic nerve endings with [3H]-noradrenaline ([3H]-NA) and the effect of electric neural stimulation (5 Hz, 0.5 ms, 8 V, 60 s) was determined in the presence of drugs which inhibit neuronal or extraneuronal uptake, or antagonize alpha-adrenoceptors. [3H]-NA overflow was significantly increased by electric neural stimulation. Perfusion with 0.1 microM phentolamine increased transmitter overflow. Infusion of 0.1 microM PGE2 reduced the [3H]-NA overflow induced by electrical stimulation. Administration of 1 microM aspirin increased the [3H]-NA overflow and PGE2 prevented this effect of aspirin. The results support the view that PGEs participate in the negative feedback of transmitter release in the isolated perfused cat heart.

Norepinephrine metabolism and clinical response to dextroamphetamine in hyperactive boys.

The 24-hour urinary catecholamine metabolites 3-methoxy-4-hydroxyphenylglycol, normetanephrine, and metanephrine were measured in 23 hyperactive boys and 13 matched healthy controls. The hyperactive children excreted lower MHPG and higher NM (low MHPG/NM ratio) amounts than in controls. The administration of d-amphetamine in the dose of 0.5 mg/kg body weight divided over two doses daily for two weeks decreased MHPG excretion in the hyperactive children. When the hyperactive children group was divided into drug responders and nonresponders according to their pre- and post-treatment scores on the Conners Teacher Questionnaire, d-amphetamine administration decreased MHPG excretion in the responders and did not change it in the nonresponders. Percent decrease in MHPG excretion correlated significantly with percent change in the hyperactivity factor of the questionnaire on the Spearman Rank Order Correlation Coefficient. Pretreatment urinary metabolites did not differentiate the responders from nonresponders. It is suggested that a relationship between CNS norepinephrine metabolism and hyperactivity exists and that d-amphetamine may achieve its therapeutic action in hyperactive children by altering CNS NE metabolism.

Iron deficiency anemia and increased urinary norepinephrine excretion.

Chronic iron deficiency in rats resulted in decreased MAO activity both in vitro and in vivo. Since MAO is an important enzyme in inactivation of catecholamines, urinary excretion of DA, NE, E, MN-NMN, and VMA was measured in 24-hour samples from 11 iron-deficient children before and after treatment with intramuscular iron. Pretreatment NE excretion was abnormally high and returned to normal (P=0.001) within one week of therapy. VMA excretion also was higher before than after treatment (P greater than 0.05), but most values were within the normal range for healthy children of comparable size. There was no significant difference between DA, E, and MN-NMN excretion before and after iron therapy. Anemic, non-iron-deficient children had normal urinary NE, E, and VMA excretion before and after transfusion. These findings suggest that the irritability, lack of attentiveness, and low performance scores of iron-deficient children may be related to alterations in catecholamine metabolic pathways secondary to dependence of MAO on adequate iron stores.