Tolerance to the sedative effect of lorazepam correlates with a diminution in cortical release and affinity for glutamate.

Benzodiazepines are anxiolytic, anticonvulsant, sedative and hypnotic compounds usually prescribed on a long-term basis. Chronic treatment with these compounds induces tolerance, which has been extensively attributed to modifications in the GABAergic neurotransmission. However, a compensatory increase in the excitatory response, named as an oppositional response, has also been put forward as a means for explaining such tolerance. Changes in the excitatory neurotransmission have been found in withdrawn rats after a long treatment with benzodiazepines but these modifications have not been conclusively studied during tolerance. In this work we studied several parameters of the glutamatergic neurotransmission in rats made tolerant to the sedative effect of 3 mg/kg (i.p.) of lorazepam (LZ). We found a decrease in the affinity of cortical NMDA receptors for (3)H-glutamate (K(D): 124.4 +/- 13.3 nM in tolerant rats, 71.6 +/- 10.4 nM in controls, P<0.05) together with a decrease in the in vitro 60 mM K(+)-stimulated cortical glutamate release (59+/- 12% vs. 153 +/- 38%, tolerant rats vs. controls, P<0.05). We conclude that tolerance to the sedative effect of LZ correlates with a decreased sensitivity for glutamate that may in turn diminish the cortical response to a chemical stimulus. Our findings constitute an evidence against the oppositional model of pharmacodynamic tolerance in this experimental condition.

Diazepam fails to potentiate GABA-induced chloride uptake and to produce anxiolytic-like action in aged rats.

The pharmacological response to benzodiazepines has been demonstrated to be different in aged individuals in comparison to adults. We studied the age-dependent changes in some of the in vitro and behavioral effects of diazepam in aged (24 months old) rats, comparing them to adults (3 months old). We evaluated the in vitro gamma-aminobutyric acid (GABA)-induced 36Cl- uptake and the diazepam potentiation of GABA-stimulated 36Cl- uptake in microsacs from cerebral cortex of both groups of animals. We found no differences in the GABA-stimulated 36Cl- uptake between adult and aged animals, and diazepam failed to potentiate GABA-induced 36Cl- flux in the aged cortical microsacs. We also examined the effect of 0.03-10 mg of diazepam on locomotor activity in an open-field test and the anxiolytic-like action of diazepam in doses ranging from 0.03 to 1 in a dark-light transition test. We observed no anxiolytic-like action of the drug in the dark-light transition test in the aged rats, while there was a shift to the left in the diminution of locomotor activity evaluated by the open-field test. We conclude that the pharmacodynamic changes observed in cortical GABA(A) receptors in aged rats could partially explain the lack of anxiolytic-like action but not the oversedation evidenced in this group of animals.

Alterations in the main steps of reverse cholesterol transport in male patients with primary hypertriglyceridemia and low HDL-cholesterol levels.

Hypertriglyceridemia is a complex pathological entity strongly connected to low HDL-C levels but controversially related to the risk of coronary artery disease. In this study, we evaluated the main steps of the antiatherogenic pathway called reverse cholesterol transport in a group of patients with primary hypertriglyceridemia and low HDL-C levels in comparison to normotriglyceridemic subjects with or without hypoalphalipoproteinemia. In patients with primary hypertriglyceridemia, low HDL-C levels were accompanied by decreased apo A-I and apo A-II concentrations. These reductions were manifested by a selective reduction in LpA-I:A-II particles. In addition, apo C-III Lp non B was found to be elevated and HDL lipid percentage composition showed a triglyceride enrichment and cholesterol depletion. The capacity of serum samples from hypertriglyceridemic patients to promote cellular cholesterol efflux was reduced, as evidenced by using two different cellular models, Fu5AH and J774 cells. This impaired cholesterol efflux promotion was also corroborated by incubations of isolated HDL fractions with Fu5AH cells. Lecithin:cholesterol acyltransferase (LCAT) activity, the driving force of reverse cholesterol transport, showed a tendency towards lower values in hypertriglyceridemic patients, but this difference was not statistically significant. Additionally, cholesteryl ester transfer protein (CETP) activity was increased in this group of patients. Therefore, hypertriglyceridemia was found to induce quantitative and qualitative alterations in HDL and its subclasses and, consequently, in some steps of reverse cholesterol transport. The abnormalities found in this antiatherogenic pathway and its promoters could constitute a possible connection between hypertriglyceridemia and atherosclerosis.

Urinary heparan sulphate is increased in normoalbuminuric diabetic patients.

Forty-nine normoalbuminuric diabetic patients were studied: 22 males and 27 females, in whom urinary heparan sulphate (HS), albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c and arterial pressure (AP) were determined. Two groups were discerned: group 1, Type 1 DM, diabetic cases (n = 16); and group 2, Type 2 DM diabetic cases (n = 33). Patients were compared with 24 healthy controls: 12 men and 12 women, who showed a mean value +/- SD of 0.36 +/- 0.18 mg/24 h HS with significant differences between males and females (0.43 +/- 0.15 versus 0.28 +/- 0.17, respectively; p = 0.02). The total population of diabetic cases rendered a mean of 0.68 +/- 0.44 and comparison with controls proved highly significant (p < 0.001). Globally, male patients had a mean of 0.82 +/- 0.48 and females 0.54 +/- 0.35, with p < 0.02. Group 1 and 2 values of HS were not significantly different. HS levels failed to correlate either with age, body mass index (BMI), time since onset of diabetes, albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c or arterial hypertension. To conclude: both normal and diabetic males eliminate a greater quantity of HS than females. Normoalbuminuric diabetic patients of both types eliminate a greater quantity of HS regardless of arterial pressure and time since onset of diabetes.

Urinary heparan sulphate is increased in normoalbuminuric diabetic patients.

Forty-nine normoalbuminuric diabetic patients were studied: 22 males and 27 females, in whom urinary heparan sulphate (HS), albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c and arterial pressure (AP) were determined. Two groups were discerned: group 1, Type 1 DM, diabetic cases (n = 16); and group 2, Type 2 DM diabetic cases (n = 33). Patients were compared with 24 healthy controls: 12 men and 12 women, who showed a mean value +/- SD of 0.36 +/- 0.18 mg/24 h HS with significant differences between males and females (0.43 +/- 0.15 versus 0.28 +/- 0.17, respectively; p = 0.02). The total population of diabetic cases rendered a mean of 0.68 +/- 0.44 and comparison with controls proved highly significant (p < 0.001). Globally, male patients had a mean of 0.82 +/- 0.48 and females 0.54 +/- 0.35, with p < 0.02. Group 1 and 2 values of HS were not significantly different. HS levels failed to correlate either with age, body mass index (BMI), time since onset of diabetes, albuminuria, creatininemia, creatininuria, creatinine clearance, HbA1c or arterial hypertension. To conclude: both normal and diabetic males eliminate a greater quantity of HS than females. Normoalbuminuric diabetic patients of both types eliminate a greater quantity of HS regardless of arterial pressure and time since onset of diabetes.

VLDL compositional changes and plasma levels of triglycerides and high density lipoprotein.

VLDL chemical composition is related to plasma levels of triglycerides and HDL-cholesterol. We evaluated patients with primary hypertriglyceridemia with or without hypoalphalipoproteinemia and subjects with normotriglyceridemia with hypoalphalipoproteinemia. The pattern observed in all the groups was an enrichment in the triglyceride content of VLDL and in apo B-VLDL. Compared to controls, LpC-III:B levels were higher in hypertriglyceridemic patients with low or normal HDL-cholesterol levels (7.3 +/- 0.6 vs. 14.9 +/- 1.8 and 12.3 +/- 2.8 mg/dl; P < 0.005 and P < 0.01, respectively) and LpE:B concentration was only increased in patients with hypertriglyceridemia and normal HDL-cholesterol levels (3.1 +/- 0.5 vs. 6.3 +/- 1.0 mg/dl; P < 0.01). The activity of the cholesteryl ester transfer protein was higher in hypertriglyceridemic patients with low HDL-cholesterol levels than in controls (380 +/- 25 vs. 262 +/- 14% cholesteryl esters/ml.h; P < 0.001). The most atypical VLDL particle was found in patients who combined an accumulation of VLDL particles and a reduction in HDL-cholesterol concentration. These two parameters represent both ends of the cholesteryl ester-triglyceride transfer, a crucial factor for VLDL chemical composition and HDL levels.

Valores de referencia de apoproteínas B100, A-I, A-II y E en mujeres premenopáusicas de la República Argentina / Reference values of apoproteins B100, A-I, A-II and E in premenopausal argentine women

Existe una relación epidemiológica entre el perfil apolipoproteico y el riesgo cardiovascular. Se han realizado pocos estudios en mujeres y menos aún en la mujeres premenopáusicas. Los objetivos del presente trabajo fueron determinar los valores de referencia en mujeres premenopáusicas clínicamente sanas de las apolipoproteínas B100, A-I, A-II y E, y correlacionarlos con los valores lipídicos de: colesterol de HDL Total (C-HDL Total), C-HDL2, C-HDL3, C-LDL y triglicéridos de VLDL (Tg-VLDL). Para ello se estudiaron 129 mujeres con perfil lipoproteico normal, de edades entre 37 y 50 años. Los valores de las apolipoproteínas fueron: apo B100: 1,17 ñ0,21 g/L (Media ñ 0,21 g/L (Media ñ DE), apo A-I: 1,34 ñ 0,24 g/L, apo A-II: 0,343 ñ 0,07 g/L y apo E: 0,065 ñ 0,017 g/L. Se obtuvieron: una media para C-HDL Total de 54,0 ñ 13,1 mg/dl, de C-HDL2 de 13,6 ñ 8,6 mg/dl y de C-HDL3 de 39,3 ñ 7,9 mg/dl. El C-LDL fue de 116,0 ñ 26,00 mg/dl. En este trabajo se informan por primera vez en Argentina los valores de referencia de concentración plasmática de apo B100, apo A-I vs C-HDL Total: 0,61 (p < 0,019), apo A-I vs C-HDL 2: 0,32 (p < 0,01), apo A-I vs C-HDL3: 0,52 (p < 0,01). La correlación de apo A-II vs C-HDL fue de 0,28 (p < 0,01). La correlación de apo E y Tg-VLDL fue de 0,25 (p < 0,025). Se calculó el índice de Breslow que evalúa el tamaño de HDL como cociente C-HDL/apo A-I + apo A-II expresados en moles, el valor obtenido fue de 21,06 ñ 4,08. Este coincide con las referencias sugiriendo que en la premenopáusica no hay cambio de tamaño en las HDL (AU)

Valores de referencia de apoproteínas B100, A-I, A-II y E en mujeres premenopáusicas de la República Argentina / Reference values of apoproteins B100, A-I, A-II and E in premenopausal argentine women

Existe una relación epidemiológica entre el perfil apolipoproteico y el riesgo cardiovascular. Se han realizado pocos estudios en mujeres y menos aún en la mujeres premenopáusicas. Los objetivos del presente trabajo fueron determinar los valores de referencia en mujeres premenopáusicas clínicamente sanas de las apolipoproteínas B100, A-I, A-II y E, y correlacionarlos con los valores lipídicos de: colesterol de HDL Total (C-HDL Total), C-HDL2, C-HDL3, C-LDL y triglicéridos de VLDL (Tg-VLDL). Para ello se estudiaron 129 mujeres con perfil lipoproteico normal, de edades entre 37 y 50 años. Los valores de las apolipoproteínas fueron: apo B100: 1,17 ñ0,21 g/L (Media ñ 0,21 g/L (Media ñ DE), apo A-I: 1,34 ñ 0,24 g/L, apo A-II: 0,343 ñ 0,07 g/L y apo E: 0,065 ñ 0,017 g/L. Se obtuvieron: una media para C-HDL Total de 54,0 ñ 13,1 mg/dl, de C-HDL2 de 13,6 ñ 8,6 mg/dl y de C-HDL3 de 39,3 ñ 7,9 mg/dl. El C-LDL fue de 116,0 ñ 26,00 mg/dl. En este trabajo se informan por primera vez en Argentina los valores de referencia de concentración plasmática de apo B100, apo A-I vs C-HDL Total: 0,61 (p < 0,019), apo A-I vs C-HDL 2: 0,32 (p < 0,01), apo A-I vs C-HDL3: 0,52 (p < 0,01). La correlación de apo A-II vs C-HDL fue de 0,28 (p < 0,01). La correlación de apo E y Tg-VLDL fue de 0,25 (p < 0,025). Se calculó el índice de Breslow que evalúa el tamaño de HDL como cociente C-HDL/apo A-I + apo A-II expresados en moles, el valor obtenido fue de 21,06 ñ 4,08. Este coincide con las referencias sugiriendo que en la premenopáusica no hay cambio de tamaño en las HDL