ANP concentrations of atria, plasma and brain in Dahl S (DS) and Dahl R (DR) rats.

In order to investigate the possible involvement of ANP in the salt dependent hypertension of the DS rats the concentrations of immunoreactive atrial natriuretic peptides (ANP-IR) in atria, plasma and brain of salt loaded and control fed DS and DR rats were determined. On a low salt diet the ANP-IR concentrations in atria, hypothalamus and basal ganglia of DS rats were higher versus DR rats. Salt loading results in a decrease of ANP-IR in left DS atria and an increase in plasma and brain stem of DS rat versus control and DR rat. The data are compared with other studies about ANP performed in Dahl rats, SHR and WKY rats. The possible reasons for the found distribution of ANP-IR are discussed.

Increase in plasma atrial natriuretic factor and right atrial area during endogenous and exogenous volume loading in healthy volunteers: effect on plasma renin activity, aldosterone and antidiuretic hormone.

The mechanisms of atrial natriuretic factor (ANF) release and the effects of ANF on plasma renin activity (PRA), plasma aldosterone and plasma antidiuretic hormone were investigated in two groups of normal subjects. One group was studied before and after endogenous volume loading produced by 30 min of head-down tilt. The other group was studied before and after an exogenous volume load in the form of 1 litre of isotonic saline infused over 30 min. Measurements made included right atrial area by two-dimensional echocardiography, PRA, plasma aldosterone, plasma antidiuretic hormone and plasma levels of ANF. There was a significant correlation between the increase in atrial area and plasma ANF concentrations after endogenous and exogenous volume loading. Levels of PRA and plasma aldosterone were suppressed significantly after exogenous volume loading but not after endogenous volume loading. The concentration of plasma antidiuretic hormone was not affected by either procedure. Short-term changes in right atrial pressure appear to regulate the plasma levels of ANF in normal people.

Modulation of atrial natriuretic peptide-induced cGMP accumulation by [Arg8]vasopressin in the cultured renal epithelial cell line, LLC-PK1.

Atrial natriuretic peptide (ANP) III stimulated the formation of intracellular cGMP in renal epithelial cells (LLC-PK1) dose dependently. Incubation of LLC-PK1 cells with [Arg8]vasopressin resulted in an increase in intracellular cAMP levels. The stimulatory effect of ANP III on the cyclic cGMP system was inhibited by coincubation with [Arg8]vasopressin in a dose-dependent manner.

Biosynthesis of 18-hydroxydeoxycorticosterone and corticosterone in adrenal tissue of rat strains with salt-dependent hypertension.

Biosynthetic patterns of 18-OH-deoxycorticosterone (18-OH-DOC) and corticosterone (B) in adrenal tissue of Wistar-rats and two rat strains with salt-dependent hypertension (Dahl-, Sabra-rats) were measured by means of quantitative HPLC-analysis. The relative activity of 18-hydroxylation is expressed as the ratio 18-OH-DOC/18-OH-DOC + B, in the following called Q. Wistar-rats show a constant product ratio Q of 0.40 +/- 0.01. Dahl-rats, however, exhibit typical differences between the two substrains. Adrenal tissue of salt-resistant (Dahl-R) rats produces significantly less 18-OH-DOC than tissue from salt-sensitive (Dahl-S) rats: Q = 0.17 +/- 0.01 (Dahl-R) vs. Q = 0.37 +/- 0.01 (Dahl-S). No such difference was observed between the two Sabra-substrains. This indicates, that other mechanisms than an altered 11 beta-18-hydroxylation are involved in the salt-dependent hypertension of Sabra-rats.

The use of a monoclonal antibody for the determination of atrial natriuretic peptides in human plasma.

A monoclonal antibody (mab) directed against alpha-human atrial natriuretic peptides (alpha-hANP) was produced. Using this mab a radioimmunoassay for the determination of hANP-like immunoreactivity in human plasma was established. To demonstrate the possible application of this radioimmunoassay for clinical diagnosis, plasma levels were measured in healthy subjects and in patients with renal failure before and after hemofiltration or hemodialysis. Plasma levels in healthy subjects ranged between less than 30 and 124 pg/ml. Mean plasma concentrations of hANP-IR in uremic subjects were 324 pg/ml before and 113 pg/ml after hemofiltration or hemodialysis.

The use of a monoclonal antibody to measure plasma atriopeptins in rat.

A monoclonal antibody with specificity for atrial natriuretic peptides (ANP) was produced, that can be used for the radioimmunological determination of ANP-immunoreactivity (ANP-IR) in rat plasma. The antibody recognizes atriopeptin I, II, III, as well as alpha-hANP and alpha-hANP fragment (7-28) and does not crossreact with ANP-fragments (13-28) and (18-28). Plasma levels of ANP-IR in conscious Wistar rats were determined before and after volume-loading. Basal plasma levels of ANP-IR were 108 +/- 12 pg/ml, and after volume-loading increased to 800 +/- 59 pg/ml.

Characteristic changes of plasma proteins in the Dahl hypertensive rat strain (DS) during the development of hypertension.

Several recent studies have reported the existence of additional plasma proteins in essential hypertensive patients and strains of genetically hypertensive rats. The aim of this work was to look for similar changes in a model of salt induced hypertension, the Dahl salt sensitive (DS) rat, using the sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis. No additional proteins were found when different staining techniques were employed (Coomassie, silver). However, during the development of hypertension a characteristic change in the plasma protein pattern of DS rats occurred, which could not be detected in the majority of normotensive control animals. Treatment with nifedipine inhibited both the development of hypertension and this specific change in the plasma proteins, in spite of continuous dietary salt loading. It is postulated that the plasma protein changes reflect a regulatory phenomenon of hypertension.

Immunoperoxidase slide assay (IPSA)--a new screening method for hybridoma supernatants directed against cell surface antigens compared to other binding assays.

A modified immunoperoxidase assay on microscope slides (IPSA) was adopted as a screening procedure for hybridoma supernatants with specificity for human lymphocyte subpopulations. The method proved to be suitable for testing a large number of hybridomas with a minimum of cells and reagents. In addition, the slide-technique yields considerable information about the type and morphology of target cells. This allows a first differentiation between cell types in the assayed preparation, e.g. between lymphocytes and monocytes. Compared to indirect immunofluorescence, solid-phase radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA) with intact cells as antigen, IPSA turned-out to be as sensitive as RIA and superior to indirect immunofluorescence and ELISA. Nevertheless, none of the assays used detected all supernatants binding to cells in the right manner and could, thus, be considered ideal. In our hands, the combination of RIA and IPSA proved to be an excellent system for screening procedures on lymphocytes.