Showing papers by "University of Luxembourg published in 1985"

Stereospecific modulation of the calcium channel in human erythrocytes by cholesterol and its oxidized derivatives

Abstract: To study the effect of cholesterol and its pathophysiologically important oxidized derivatives (OSC) on the calcium entry channel, the human red blood cell was used as a model system. The calcium ejecting adenosinetriphosphatase (ATPase) was inhibited by vanadate. The cells were loaded with OSC at concentrations between 1.25 X 10(-5) and 25 X 10(-5) mol/l. 22-Hydroxycholesterol, cholestan-3 beta,5 alpha,6 beta-triol, 5 alpha-cholestan-3 beta-ol,3 beta,5 alpha-dihydroxycholestan-6-one and 3 beta-hydroxy-5 alpha-cholestan-7-one stimulated 45Ca2+ influx by up to almost 90%, whereas 25-hydroxycholesterol, 7 beta-hydroxycholesterol, 20 alpha-hydroxycholesterol and 7-oxocholesterol inhibited influx by up to 75%. Both stimulation and inhibition were dependent on the amount of OSC incorporated into the membrane. More than 90% of the total modification of calcium influx by OSC was accounted for by an influence on the nitrendipine-inhibitable part of influx. Enrichment of cholesterol in the membrane greatly stimulated, and cholesterol depletion inhibited, Ca2+ influx. These results demonstrate that cholesterol and its oxidized derivatives are able to modulate the calcium channel in human red blood cells in a highly stereospecific manner.

Compliance with salt restriction as a limiting factor in the primary prevention of hypertension.

Abstract: It is an important but still unresolved question whether reduction of salt intake in the offspring of hypertensives (a high risk group) prevents the development of the disease. Therefore, 178 offspring (14-26 years old) of hypertensives were enrolled in a 2-year pilot trial aimed mainly at a reduction in salt consumption. For the intervention group (n = 99) a behavioural approach was chosen with extensive counselling by experienced dietitians. The controls (n = 79) received no continuous dietary advice. Both groups showed a small decline in sodium intake over time, but the differences between the two groups were not significant. Division into subgroups with and without sodium reduction revealed no differences in blood pressure. We conclude that the inherent resistance to any change of lifestyle among healthy subjects may require new and more comprehensive motivational approaches.

High density lipoproteins--modulators of the calcium channel?

Abstract: It has recently been shown that human red blood cells possess a voltage-independent calcium channel which can be influenced by in vitro modification of the membraneous cholesterol content. To determine whether there is also a link between plasma lipids and the calcium influx through this channel under in vivo conditions, the calcium influx was measured in red blood cells from 51 male donors (aged 41 +/- 5 years). The influx through the channel was defined as the nitrendipine (15 mumol/l)-inhibitable part of 45Ca2+ influx. The Ca(2+)-ejecting ATPase was inhibited by vanadate. The results demonstrate a strong inverse relationship (r = -0.81; P < 0.001) between the plasma concentration of high density lipoproteins (HDL) and 45Ca2+ influx. No significant correlation was found between 45Ca2+ influx and triglycerides, low density lipoproteins (LDL), very low density lipoproteins (VLDL), total plasma cholesterol or extracellular electrolytes (K+, Na+, Ca2+, Mg2+). The results indicate that HDL are involved in the modulation of the calcium channel and provide a link between the cellular cholesterol turnover and the calcium influx in the pathogenesis of atherosclerosis and hypertension.

A simple and effective method to teach patients about high blood pressure and obesity.

Abstract: It is an open question whether information about hypertension and obesity increases compliance with therapy. Nevertheless, patients increasingly demand precise but simple and comprehensive information. A simple slide programme is described which can be demonstrated in any waiting room. The learning effect was assessed in 1083 subjects, of whom 485 had seen the programme completely; 256 subjects served as controls. The percentage of subjects with good or excellent knowledge about hypertension and obesity rose from 22.8% in the controls to 64.2% in the experimental group. Age was the only factor influencing learning, but this was of no great importance in subjects under 70. In particular, social status did not have any significant effect on learning. This programme may be an ideal tool to inform patients about hypertension and obesity and to study the influence of information on compliance with therapy.