1. In the rectum and distal nephron, sodium reabsorption is mediated by the amiloride-sensitive epithelial sodium channel (ENaC). The ENaC-mediated sodium transport is electrogenic and creates an amiloride-sensitive transepithelial potential difference (PD). 2. We have evaluated the salt- and angiotensin (Ang)II-dependent variations in amiloride-sensitive rectal PD in mice and assessed their relationship with renal sodium handling. 3. Rectal PD was measured in vivo in mice maintained on a medium-, low- or high-sodium diet. On a medium-salt diet, the mean (+/- SEM) amiloride-sensitive PD was larger in the afternoon than in the morning (-26.1 +/- 0.9 and -11.2 +/- 0.7 mV, respectively; P = 0.001), indicating a circadian cyclicity. Rectal PD increased on a low-sodium diet and decreased on a high-sodium diet. 4. Amiloride-sensitive rectal PD correlated significantly with the urinary Na+/K+ ratio (P < 0.001) and with sodium reabsorption in the distal nephron as measured by the lithium clearance technique (P < 0.001). 5. In mice treated with an AngII AT1 receptor antagonist, amiloride-sensitive rectal PD was increased in the afternoon compared with controls (-32.8 +/- 2.0 vs -24.4 +/- 0.9, respectively; P < 0.001). 6. At high doses, AngII decreased the amiloride-sensitive rectal PD and this effect was blunted by an AT1 receptor antagonist. 7. These results show the presence of a salt-dependent daily cyclicity of sodium transport in the mouse rectum that follows circadian changes in sodium handling in the distal nephron. Angiotensin II appears to modulate this diurnal pattern of rectal amiloride-sensitive sodium transport.

Angiotensin II↗

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Objective evaluation of two markers of HIV-1 infection (p24 antigen concentration and CD4+ cell counts) by a self organizing neural network.

The aim of the present work is to obtain groups of patients with similar profiles of p24 antigen concentration and of CD4+ cell counts. These two markers were chosen because their evaluation represents a significant step in the clinical follow up of HIV-1 infected subjects. The detection methods for p24 antigen concentration and for CD4+ cell counts are well assessed and guarantee easy reproducibility of data obtained in different laboratories. A set of observations with the same time intervals were derived from a continuous function obtained for each patient by a back-propagation neural net trained on the raw data from the patient. The classifications were obtained by a Kohonen neural net trained in three ways: with p24 antigen profiles only, with CD4+ cell count profiles only and with both sets of profiles. The results show that the clustering fashion of the two parameters closely resembles the clustering fashion of CD4+ only, rather than that of p24Ag, both with reference to cluster formation and with reference to distances between clusters.

Acquired Immunodeficiency Syndrome↗

PubMedDate not supplied

[Influence of moderate body weight excess on the nycthemeral pattern of blood pressure, renal function and sodium and water excretion in patients with essential hypertension].

Obesity is a risk factor for arterial hypertension. We studied the relationships between the body mass index (BMI) and the nycthemeral pattern of blood pressure (BP), renal function and sodium and water excretion (EX) in a group of 25 moderately hypertensive untreated men (41 +/- 2 y, 80 +/- 3 kg). Subjects were given a high sodium diet (6 g NaCl added to their usual diet, daily EX=200 mmol). On the 7th day, BP was monitored during 24 h and urine collected in 2 fractions (day=D, 8:00-22:00 and night=N, 22:00-8:00). Subjects were a posteriori divided into 2 groups according to the median BMI (26 kg/m2): Group 1, n=12, BMI 23.2 +/- 0.6 (mean +/- SEM) and Group 2, n=13, BMI 29.2 +/- 0.5 kg/m2. No difference was observed between the two groups for age, 24 h urine and sodium EX, or systolic and diastolic BP. However, heart rate was significantly higher during N in Group 2 (66 +/- 2 vs 57 +/- 2 b/min, p=0.012). Na and water EX were significantly higher during D than during N in Group 1, but lower during D than during N in Group 2. Creatinine clearance was higher in Group 2 than in Group 1 especially during N (D+29%, p=0.013; N+49%, p<0.001). In Group 2, subjects concentrated their urine more than in Group 1, as evaluated from the urine/plasma creatinine ratio (+49%, p=0.019). This ratio was positively correlated to BMI during D (r=0.561, p=0.004) but not during N. These results show that the glomerular hyperfiltration associated with overweight is more intense at night and that moderately overweight hypertensives have a reduced sodium and water EX during the day and a compensatory larger EX at night. The reduced diurnal EX goes along with an increased urine concentration. The nocturnal rise in EX is concomittant with a rise in heart rate. Given the growing health problems linked to obesity and hypertension, these results open a new field for the understanding of the difficulty to excrete sodium in this condition.

Adult↗

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