Mechanisms responsible for the altered cardiac repolarization dispersion in experimental hypothyroidism.

AIMS: To identify the causes for the inhomogeneity of ventricular repolarization and increased QT dispersion in hypothyroid mice. METHODS: We studied the effects of 5-propyl-2-thiouracil-induced hypothyroidism on the ECG, action potential (AP) and current density of the repolarizing potassium currents I(to,fast), I(to,slow), I(K,slow) and I(ss) in enzymatically isolated myocytes from three different regions of mouse heart: right ventricle (RV), epicardium of the left ventricle (Epi-LV) and interventricular septum. K(+) currents were recorded with the patch-clamp technique. Membranes from isolated ventricular myocytes were extracted by centrifugation. Kv4.2, Kv4.3, KChIP and Na/Ca exchanger proteins were visualized by Western blot. RESULTS: The frequency or conduction velocity was not changed by hypothyroidism, but QTc was prolonged. Neither resting membrane potential nor AP amplitude was modified. The action potential duration (APD)(90) increased in the RV and Epi-LV, but not in the septum. Hypothyroid status has no effect either on I(to,slow), I(k,slow) or I(ss) in any of the regions analysed. However, I(to,fast) was significantly reduced in the Epi-LV and in the RV, whereas it was not altered in cells from the septum. Western blot analysis reveals a reduction in Kv4.2 and Kv4.3 protein levels in both the Epi-LV and the RV and an increase in Na/Ca exchanger. CONCLUSION: From these results we suggest that the regional differences in APD lengthening, and thus in repolarization inhomogeneity, induced by experimental hypothyroidism are at least partially explained by the uneven decrease in I(to,fast) and the differences in the relative contribution of the depolarization-activated outward currents to the repolarization process.

Type 1 diabetes alters brain cannabinoid receptor expression and phosphorylation status in rats.

One of the most common symptoms of diabetes is extreme hunger, but the brain mechanism underlying this hyperphagia is unknown. The endocannabinoid system has emerged as one of the main food intake regulators in the brain. However, the effects of type 1 diabetes on the endocannabinoid system are not completely known. Thus, the aim of the present work is to establish the possible alterations induced by type 1 diabetes on the brain endocannabinoid system in rats. Western blot and immunocytochemistry were used to measure CB1 and phosphorylated CB1 receptor expression in several prosencephalic regions in streptozotocin-induced type 1 diabetic rats. Serum leptin levels were measured by ELISA. CB1 receptor expression was increased in striatum and hypothalamus of diabetic animals, with no changes in other brain areas studied. CB1 receptor phosphorylation was also increased in the same brain areas. Type 1 diabetes induced significant weight loss, and serum leptin levels were severely decreased. These results reinforce the possible role of the CB1 receptor as a pharmacological target for the clinical management of appetite in diabetic patients.

Diabetes-induced biochemical changes in central and peripheral catecholaminergic systems.

A great variety of alterations have been described in the nervous system of diabetic animals. They are named as diabetic neuropathy and affect the brain, spinal cord and peripheral nerves. In diabetic animals, plasma and tissue catecholamine levels have been reported to be increased, decreased or unchanged, and these disparities have been explained by differences in the tissues selected, severity or duration of diabetes. Dopamine, norepinephrine and epinephrine from different tissues were extracted by absorption onto alumina, and measured by high performance liquid chromatography with electrochemical detection. We found that diabetes alters catecholaminergic systems in a highly specific manner. The dopamine content is reduced in the dopaminergic nigrostriatal system only. Norepinephrine is differently altered in several areas of the sympathetic nervous system. It is increased in cardiac ventricles, and decreased in stellate ganglia and the blood serum. However, it is not altered in the central nervous system. Finally, epinephrine is only altered in the adrenal gland where it is increased, and in the serum where it is reduced. Our results suggest that diabetes reduces the activity of the nigrostriatal dopaminergic system. Changes found at the sympathoadrenal level could be explained by reduced norepinephrine and epinephrine synthesis, with increased storage due to a reduced release from synaptic vesicles.

Virtual automation.

Total laboratory automation (TLA) can be substituted in mid-size laboratories by a computer sample workflow control (virtual automation). Such a solution has been implemented in our laboratory using PSM, software developed in cooperation with Roche Diagnostics (Barcelona, Spain), to this purpose. This software is connected to the online analyzers and to the laboratory information system and is able to control and direct the samples working as an intermediate station. The only difference with TLA is the replacement of transport belts by personnel of the laboratory. The implementation of this virtual automation system has allowed us the achievement of the main advantages of TLA: workload increase (64%) with reduction in the cost per test (43%), significant reduction in the number of biochemistry primary tubes (from 8 to 2), less aliquoting (from 600 to 100 samples/day), automation of functional testing, drastic reduction of preanalytical errors (from 11.7 to 0.4% of the tubes) and better total response time for both inpatients (from up to 48 hours to up to 4 hours) and outpatients (from up to 10 days to up to 48 hours). As an additional advantage, virtual automation could be implemented without hardware investment and significant headcount reduction (15% in our lab).

Procesos de automatización. Estructuras Core Lab / Processes of Automation. Core Lab Structures

No disponible

Restoration of cardiac transient outward potassium current by norepinephrine in diabetic rats.

In cardiac ventricle, the density of the transient outward potassium current, Ito, is clearly related to sympathetic nervous system integrity. This sympathetic regulation of Ito expression may be greatly significant to the genesis of cardiac complications of several diseases such us diabetes mellitus. Autonomic neuropathy, including cardiac neuropathy, is a complication of chronic diabetes. The objective of the present study was to identify the possible role of cardiac sympathetic neuropathy in the reduction of Ito current density in diabetic ventricular myocardium. Thus, we employed the patch-clamp technique to test whether Ito can be restored in diabetic myocytes incubated with norepinephrine. We also measured, using HPLC, the catecholamine content of the stellate ganglion, which is responsible for cardiac sympathetic innervation, in normal and diabetic animals. The main result of the present study was to show that a 24-h incubation of diabetic cells with norepinephrine restores Ito density to control values. The restoration of Ito current density by norepinephrine suggests that the diabetes-induced reduction of Ito is at least partially attributable to a reduced trophic effect of norepinephrine on the expression of Ito.

Effects of acute xylene exposure on the enkephalinergic neuromodulatory system in rats.

Xylene is a neurotoxic organic solvent widely used in industry. However, the neurochemical mechanism of its action on the central nervous system is to date relatively unknown. In this work, the effect of subacute xylene exposure on met-enkephalin like immunostaining in different brain regions is described. Acute treatment with xylene generates a reduction in immunostaining for met-enkephalin in the globus pallidus, the olfactory tubercule and the hypothalamic medial preoptic area, without changes in the parietal cortex, caudatus-putamen and the central amygdaloid nuclei. It is suggested that enkephalins could play a role in xylene neurotoxic mechanism in the brain.

Lys- and Leu-aminopeptidase activity after acute toluene exposure in the rat brain.

Changes in Lys- and Leu-aminopeptidase activities in several brain regions of the rat, after acute toluene administration, are described in this research. Aminopeptidase activity has been suggested as a candidate regulator of the degradation of several neuroactive peptides. Lys-aminopeptidase activity was significantly decreased in the thalamus, amygdala, and medulla oblongata. Leu-aminopeptidase activity was significantly decreased in the thalamus and cerebellum. It is suggested that these aminopeptidase activities could play a part in the mechanism of toluene neurotoxicity.

[Is the renin-angiotensin system implicated in the hypertensive effect of a water-soluble tissue extract?]. / Está el sistema renina-angiotensina implicado en el efecto hipertensor de un extracto tisular hidrosoluble?

A deproteinized hydrosoluble splenic extract, which produces a hypertensive effect, injected in rats intravenously is described. The pressure action is very similar to the synthetic angiotensin II, and the (Sarcosine1-Isoleucine8)--angiotensin II, a competitive antagonist, produced partial inhibition of both responses. There were no significant differences between control and experimental rats in the plasmatic levels of angiotensin II, aldosterone and ADH. Therefore, the splenic extract does not seem to release these hormones included in the renin-angiotensin pathway. Significant Angiotensin II levels were detected in the splenic material. These results support the view that forty per cent of the pressure action is due to Angiotensin II present in the extract.

[Inhibiting effect of (sarcosine-1-isoleucine-8)-angiotensin II in anesthesized rats]. / Acción inhibidora de la (sarcosina-1-isoleucina-8)-angiotensina II en rata anestesiada.

The peptidic sequence (Sarcosine-1-Isoleucine-8)-Angiotensin II has been demonstrated to be an in vitro specific and competitive antagonist of the Angiotensin II action. The present results show it to be a competitive antagonist also in vivo since pA2 values are similar, always reaches a 100% response on increasing the Angiotensin II dose, and when relating log (DR-1) and log dose of agonist, the slope is very near to one (0.925).

H1-histamine receptors may mediate the contractile response of guinea-pig ileum to 'histamine-free' splenic extracts.

A water-soluble splenic factor, which produces a contractile response of the guinea-pig ileum, that is resistant to cholinoceptor and adrenoceptor antagonists is described. The ileal contractions elicited by the splenic extract showed some significant differences from those elicited by 5-hydroxytryptamine. The responses to splenic extract were not affected by the D-tryptamine-receptor antagonist, methysergide. The effect of the splenic extract on the guinea-pig ileum was similar to that of histamine. The H1-histamine antagonists, (+)-chloropheniramine and diphenhydramine, caused a parallel shift to the right of the splenic extract dose-response curve without suppression of the maximum response. A pA2 value of 8.97 +/- 0.03 for (+)-chloropheniramine and 7.55 +/- 0.1 for diphenhydramine was calculated. Significant histamine levels, as determined by fluorometric methods, could not be detected in the splenic extract. Likewise, the splenic factor did not release histamine from the intestinal preparation. These results support the view that: (i) the splenic factor acts through H1-histamine receptors; (ii) it is not histamine; (iii) it does not have any histamine releasing effect on the ileal smooth muscle.