Search PubMed⌕ Search

Biomedical subjects

P Esbrit

Publications and source records attributed to P Esbrit.

70 records · Page 4Linked to original sources
PubMed1980

A C-terminal radioimmunoassay for human parathyrin.

Several features concerning the parathyrin (PTH) radioimmunoassay (RIA) in human serum have been considered. The bovine hormone (bPTH) was used as standard and to obtain the radioiodinated tracer and the antisera employed exhibited a C-terminal specificity. A modification of the classical Greenwood and Hunter method was used to label bPTH, based on the sequential addition of small amounts of Chloramine-T to the solution containing the hormone to prevent ovariodination. The purification by Quso G32 followed by a gel-filtration step, produced a suitable tracer for a highly sensitive RIA. Due to unespecific effects from serum in the incubation medium, serum concentration was rendered uniform in all of the assay tubes prior to the addition of the separation mixture (charcoal-dextran). The greatest sensitivity reached was 16 pg of bPTH in the incubation mixture with Ch 4M antiserum. This antiserum allows detection of immunoreactive PTH in the majority of normal subjects and has applicability to a wide range of bone disturbances.

Humans↗
PubMedDate not supplied

Parathyroid hormone-related protein as a renal regulating factor. From vessels to glomeruli and tubular epithelium.

Parathyroid hormone (PTH) and PTH-related protein (PTHrP) produce similar biological effects through the PTH/PTHrP receptor. Less is known about the physiological role of PTHrP, which was first identified as the agent of the humoral hypercalcemia of malignancy. Despite the widespread production of PTHrP in healthy individuals, the concentration of the protein is below the detectable limit of current assays, suggesting that PTHrP normally functions locally in an autocrine or paracrine manner. Thus, some differences in their biological activities have been described and they may be related to the presence of different receptors. In this regard, a second receptor that binds selectively to PTH has also been found. Recent studies have demonstrated the expression of both PTH/PTHrP receptor and protein in the renal glomeruli. Moreover, there are convincing data that support a direct role of PTH and PTHrP in modulating renal blood flow and glomerular filtration rate. This multifunctional protein, PTHrP, also has a proliferative effect on both glomerular mesangial cells and tubular epithelial cells. Increases in the expression of PTHrP have been observed in several experimental models of nephropathies, suggesting that PTHrP upregulation is a common event associated with the mechanism of renal injury and repair.

Glomerular Filtration Rate↗
PubMedDate not supplied

Biological properties of a renotropic protein present in plasma of uninephrectomized rats.

The biological characteristics of a kidney growth factor (KGF) from uninephrectomized rat plasma have been studied. A crude preparation of this factor [Nephrol. Dial. Transplant. 4: 334-338, 1989] was further purified by hydrophobic interaction HPLC and gel filtration. KGF was found to be a heat- and trypsin-resistant protein. This factor stimulated dose-dependently DNA synthesis by the mouse kidney in vivo, and by either rat renal tubules or serum-deprived LLC-PK1 cells, in vitro. KGF also increased protein synthesis in these cells, in a dose-dependent manner. Moreover, KGF stimulated sodium uptake by these cells, associated with the maximal increase of protein synthesis. Our findings indicate that KGF is a potent renotropic protein which can play a key role in the renal compensatory growth after uninephrectomy.

Animals↗
PubMedDate not supplied

Further studies on the characterization of a renotropic activity detected in uninephrectomized rat plasma.

Using chromatographic techniques, we have purified a peptide responsible, at least in part, for the renotropic activity detected in 24-hour uninephrectomized adult rat plasma. The most purified material behaved as a single component when analyzed by reversed-phase HPLC. The purified factor stimulates DNA synthesis in isolated rat proximal tubules and proximal tubular cell (LLC-PK1) cultures. This effect was abolished by pretreatment with protease K, with an intracellular calcium chelator or with indomethacin. This factor was also mitogenic for rat mesangial cells. In contrast, neither Madin-Darby canine kidney cells nor rat liver cells responded to the growth factor. Using the same purification procedure, a bioactive factor with an amino acid composition almost identical to that of this renotropic peptide was isolated from sham-operated or normal rat plasma. However, only uninephrectomized plasma after gel filtration showed renotropic activity, which was inhibited by the corresponding chromatographic fraction from sham-operated plasma. Our findings suggest that a change in the concentration of a circulating inhibitor(s) appears to account for the differences in the activity of sham-operated or control plasma and uninephrectomized plasma on the growth of renal cells.

Animals↗
PubMedDate not supplied

Transforming growth factor-beta and its receptors in rabbit renal proximal tubules after uninephrectomy.

Transforming growth factor-beta (TGF beta) and its receptors were studied in proximal tubules isolated from rabbit renal cortex at different times after uninephrectomy (UNX). Scatchard analysis of TGF beta-binding data in proximal tubules from control kidneys revealed two types of binding sites, with Kd 21 and 208 pM, and Bmax 33 and 104 fmol/mg protein, respectively. Kd values were similar in these animals at 1 or 2 weeks after either UNX or sham operation (SNX). However, Bmax increased in parallel with the observed increase in the protein/DNA ratio of the proximal tubules at 2 weeks after UNX. In contrast, [125I]-insulin binding per milligram of protein was lower in proximal tubules from uninephrectomized compared to sham-operated animals within the same time period. Affinity labeling of [125I]-TGF beta 1-binding sites in proximal tubules from either sham-operated or uninephrectomized rabbits displayed two labeled proteins with apparent molecular weights of > 143 and 43 kD. We found an increased TGF beta bioactivity in the conditioned medium of proximal tubules at 2 weeks following UNX. This protein increase was associated with an increased TGF beta 1 mRNA expression in these tubules. In contrast, no significant changes in TGF beta bioactivity were observed in rabbit glomeruli conditioned medium or in rabbit urine at this time period after UNX. Our data indicate that hypertrophy of the proximal tubule is associated with an increased TGF beta production and a lack of downregulation of its receptors in this nephron portion.

Animals↗
PubMedDate not supplied

[Basic principles of radioimmunoanalysis].

The authors review the principal characteristics of radioimmunoassay (R.I.A.), in grounds of the so-called "saturation analysis" techniques, which are of increasing interest among the chemical laboratory procedures. They study each element of R.I.A. separatedly, and finally they make a brief display of the different applications of radioimmunoassay stressing its significance in the endocrinological field.

Antibodies↗