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Biomedical subjects

F Pinet

Publications and source records attributed to F Pinet.

At least 19 recordsLinked to original sources
PubMed1995

Opposite regulation of renin gene expression by cyclic AMP and calcium in isolated mouse juxtaglomerular cells.

A quantitative reverse transcriptase-polymerase chain reaction for mouse renin mRNA was utilized to study the influence of classic second messenger molecules on renin mRNA levels in primary cultures of juxtaglomerular (JG) cells isolated from the kidneys of C57/B16 mice. We found that forskolin (3 microM), an activator of adenylate cyclase led to proportional increases of renin secretion and renin mRNA levels. The nitric oxide (NO) donor, sodium nitroprusside (100 microM), stimulated both renin secretion and renin gene expression, the effect on secretion being stronger than that on renin mRNA levels. An increase of the extracellular concentration of calcium from 0.5 to 3 mM led to a transient inhibition of renin secretion, followed by a marked stimulation of secretion and to a continuous suppression of renin mRNA levels. These were also decreased by the calcium ionophore A 23187 (1 microM). The membrane permeable 8-bromo-cyclic GMP (100 microM) inhibited basal renin secretion without an effect on renin mRNA levels. The phorbol ester phorbol-12-myristate-13-acetate (1 to 100 nM), which was used to stimulate protein kinase C activity, had no significant effects on renin secretion and renin mRNA levels, neither alone nor in combination with forskolin. These findings suggest that cAMP, NO and calcium are effective regulators of renin gene expression in renal JG cells, in a way that cAMP and NO are stimulators and calcium acts as an inhibitor. Moreover, in these acute experiments there appears to be no obligatory link between the secretion and the expression of renin, suggesting that both parameters are separately regulated.

Animals↗
PubMed1994

A mutant renin gene in familial elevation of prorenin.

A case of familial elevation of plasma prorenin levels was discovered during an epidemiological survey of a Dutch population. Trypsin-activated prorenin was elevated in the 58-year-old father, his son, and one of his sisters. All family members were normotensive and had normal plasma renin activities. Exon sequencing of the renin gene of the proband and of his son after polymerase chain reaction amplification identified a point mutation in the last exon of the gene (exon 10). A cytosine to thymine transition creates a premature stop codon at position 387 resulting in a truncated form of renin with 20 amino acids deleted from the carboxyl terminus. All family members presenting high levels of plasma prorenin were heterozygous for the mutation. Expression vectors carrying normal or mutated renin cDNA were transiently transfected into AtT-20 cells to test in vitro the functional consequences of this mutation. Measurements of renin activity and pulse-chase experiments indicated that the truncated renin is inactive and not secreted from transfected cells. We hypothesize that the abnormal gene product of the mutated allele alters renin sorting and propose that plasma prorenin elevation may result from a compensatory mechanism.

Animals↗
PubMed1994

Co-expression of PC2 and proenkephalin in human tumoral adrenal medullary tissues.

Expression of PC2, a Kex2-related protease, and of one of its possible substrates, proenkephalin, was examined in normal adrenal glands (n = 7) and pheochromocytomas (n = 20). PC2 could only be detected in normal adrenal glands using the sensitive RT/PCR technique. By Northern blot, PC2 and proenkephalin were expressed in 85% and 90% of the 20 pheochromocytomas studied, respectively. Moreover, in situ hybridization and immunohistochemistry confirmed expression of PC2 in human tumoral adrenal medullary tissue. These results show for the first time expression of PC2 in human pheochromocytomas which may be involved in the processing of proenkephalin.

Adrenal Gland Neoplasms↗
PubMed1994

Expression of PC2 and PC1/PC3 in human pheochromocytomas.

Expressions of two Kex2-related proteases, Pc2 and PC1/PC3, and of one of their possible substrates, proenkephalin, were examined in normal (n = 7) and various pathological (n = 48) human adrenal tissues. Northern blot analysis detected the expression of these genes in pheochromocytomas only. In the 20 pheochromocytomas studied with this technique, PC2, PC1/PC3 and proenkephalin were expressed in 85%, 50% and 90%, respectively. The presence of PC2 and PC1/PC3 was further confirmed using the sensitive RT/PCR techniques. Other evidence of human tumoral adrenal medullary PC2 expression was provided by in situ hybridization and immunohistochemistry. In addition, proenkephalin was expressed only in the pheochromocytomas expressing PC2 and/or PC1/PC3. These results demonstrate that functional Kex2-related endoproteases are expressed in human pheochromocytomas and may be involved in the processing of proenkephalin.

Adrenal Gland Neoplasms↗
PubMed1994

cis-regulatory elements and trans-acting factors directing basal and cAMP-stimulated human renin gene expression in chorionic cells.

Much knowledge was accumulated in the regulation of plasma renin activity and renin secretion during recent years. However, the mechanisms of renin gene transcription, especially for the human gene, have been poorly studied because of the lack of cell lines expressing renin. Cells derived from chorion tissue were used to study renin gene transcription because these cells express renin and regulate renin secretion in a similar way to JG cells. The present study was performed to determine the cis-regulatory elements and the trans-acting factors involved in human renin gene expression using chorionic cells. Transient DNA transfections were performed with various constructs containing the 5'-flanking region of the human renin gene. 5'-Deletion analysis of the human renin promoter (from -2616 to -67 bp) revealed the presence of two proximal negative cis-regulatory elements between -374 and -273 bp and between -273 and -137 bp. These elements were not present in a non-renin-producing cell line, JEG-3 cells. DNase I footprinting revealed that two sequences located within these regions bind trans-factors present in chorionic cellular nuclear extract: AGE3-like sequence (-293/-273) and apolipoprotein A1 regulatory protein-1-like sequence (-259/-245). The first 110 bp of the renin promoter were sufficient to direct specific expression in chorionic cells and contained two footprints sharing homology with ets (-29/-6) and pituitary-specific factor (Pit-1) (-70/-62) sequences. Furthermore, one footprint (-234/-214) contained the sequence TAGCGTCA, which shares strong homology to the cAMP-responsive element (CRE) binding site. Gel shift analysis showed specific DNA/protein complexes within this region, which were displaced by the somatostatin consensus CRE. Finally, luciferase analysis of 5'-deletion mutant revealed that -273 to +16 bp of the renin promoter was sufficient to confer complete forskolin stimulation, whereas deletion to -130 (deletion of the CRE) decreased cAMP responsiveness by 50% and those to -67 bp (deletion of the CRE and Pit-1-like sequences) suppressed it. Thus, these latter two sequences probably act together to confer complete cAMP responsiveness.

Base Sequence↗
PubMed1994

Renin-secreting tumors.

An analysis of the renin-secreting tumors published in the literature suggests the diagnosis of JGC tumor should be evoked systematically in a young patient with severe hypertension and hypokalemia in whom a renovascular lesion has been eliminated by arteriography. A very high PRA usually is observed and blood pressure drops during converting enzyme treatment. Under acute administration of captopril, plasma renin may or may not increase, showing the inconsistency of the secretory autonomy of the tumor. The most useful examination for the localization of the tumor is the CT scan. Excessive renin production may provoke vascular lesions, left ventricular hypertrophy, and impairment of renin function that all disappear after surgical treatment, at the time when blood pressure returns to normal. Primary reninism has great physiologic importance for the hypothesis that favors the essential role of the kidney in determining the level of blood pressure. It can be considered as a unique, purely renin-dependent form of hypertension. This syndrome has no experimental equivalent and is the most caricatural form of other renin-dependent hypertension, such as renovascular disease, and probably some other forms of essential hypertension. The discovery of a renin-secreting tumor therefore constitutes a life-saving diagnosis for the patient, a subject of reflection for the specialist, and a useful tool for studies of the general mechanisms involved in enzyme biosynthesis and tumoral endocrine cell function.

Adenocarcinoma↗
PubMed1993

Regulation of human renin secretion and renin transcription by quantitative PCR in cultured chorionic cells: synergistic effect of cyclic AMP and protein kinase C.

A quantitative PCR was developed to measure human renin mRNA in chorionic cells under various stimuli. An internal standard consisting of a mutated renin mRNA with an insertion of 60 bp was designed to quantify the reaction. Quantitative PCR is a suitable tool for studying human renin gene transcription from a low number of cells. Forskolin alone had no effect on either renin mRNA levels or renin production whereas 10(-7)M PMA stimulated renin mRNA levels and renin production 5- and 2.6-fold, respectively, after 24 hours incubation. PMA and forskolin acted synergistically to increase both renin mRNA levels and renin production in a dose-dependent manner.

Base Sequence↗
PubMed1993

Detection of renin mRNA in aldosterone-producing adenomas by polymerase chain reaction.

1. Ribonucleic acid (RNA) was extracted from two normal human adrenal cortices and from five aldosterone-producing adenomas (APA). 2. The five APA could be categorized, on the basis of in vivo aldosterone responsiveness to angiotensin infusion and upright posture, into two APA responsive to both stimuli, two responsive only to angiotensin infusion, and one unresponsive to either stimulus. 3. RNA was reverse transcribed and coamplified by polymerase chain reaction (PCR) with an internal standard of renin complementary DNA (cDNA) containing a 60 base pair insertion. Renin mRNA in the APA was compared with normal adrenals. 4. Renin mRNA was greater than normal in the two APA responsive to both stimuli and less than, or similar to normal, in the two APA responsive only to angiotensin infusion. Renin mRNA was also less than, or similar to normal, in the APA unresponsive to either stimulus. 5. These findings support a possible role for adrenal renin in the development and biochemical behaviour of angiotensin-responsive APA.

Adenoma↗
PubMed1993

Renin mRNA quantification using polymerase chain reaction in cultured juxtaglomerular cells. Short-term effects of cAMP on renin mRNA and secretion.

The aim of the present study was to set up a method to quantify renin mRNA levels in mouse renal juxtaglomerular cells, the main physiological site of renin synthesis. Because of the scarcity of the cells, a quantitative polymerase chain reaction had to be developed to measure renin mRNA. Juxtaglomerular cells were isolated and cultured for 2 days under various conditions, and renin mRNA was measured directly from the cytoplasm of the cultured cells without prior RNA purification. An internal standard consisting of a mutated renin mRNA with an insertion of 60 bp was designed to quantify the reaction, ensuring an identical detection and amplification efficiency to the target RNA. Renin mRNA could be precisely quantified between 0.6 and 20 pg, thus allowing its detection in approximately 5000 juxtaglomerular cells. Forskolin, an activator of adenylate cyclase, led to a concentration-dependent maximal threefold increase in renin mRNA in the cultures after 20 hours of incubation. The half-maximal effective dose was 3 x 10(-7) mol/L. The effect of forskolin was mimicked by 10(-5) mol/L isoproterenol, a beta-receptor agonist, and by 10(-5) mol/L isobutylmethylxanthine. A time-course study showed a rapid increase in renin mRNA within 3 hours after forskolin and isoproterenol addition. Renin secretion in the culture medium was measured in parallel and found to be stimulated by both agents. These results show that quantitative polymerase chain reaction is a suitable tool for studying renin gene expression in cultured juxtaglomerular cells. Our findings indicate that cAMP is a potent and fast activator of renin gene transcription and renin secretion in renal juxtaglomerular cells.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Expression of steroidogenic enzyme messenger ribonucleic acids and corticosteroid production in aldosterone-producing and "nonfunctioning" adrenal adenomas.

"Nonfunctioning" adrenal adenomas are often diagnosed in patients without recognizable clinical symptoms of adrenocortical hyperfunction. The objective of this study was to determine directly the steroidogenic activity of such adenomas (n = 12) and compare them histologically and functionally to normal human adrenals (n = 6) and aldosterone-producing adenomas (n = 15). The histological appearances of nonfunctioning and aldosterone-producing adenomas were surprisingly similar. Nonfunctioning adrenal adenomas expressed all mRNAs of P450scc, P450c17, P450c21, adrenodoxin, and adrenodoxin reductase with relative levels comparable to those found in normal adrenals. Consistent with their hormone-producing nature, these adenomas had cortisol and aldosterone contents as high as those in normal adrenal tissues, a significantly (P < 0.05) increased 17-hydroxyprogesterone content, and a disproportionally low expression of P450c21 mRNA compared to aldosterone-producing adenomas. Cells isolated from both aldosterone-producing and nonfunctioning adrenal adenomas exhibited highly ACTH-sensitive cortisol and aldosterone production, suggesting again the presence of both zona glomerulosa-like and zona fasciculata-like steroidogenesis in these adenoma tissues. These results indicate that so-called nonfunctioning adrenal adenomas are not without steroidogenic activity. Therefore, the assumption that adrenal adenomas are entirely nonfunctioning in the absence of recognizable hormonal hyperfunction may not be correct.

Adenoma↗
PubMed1992

Calmodulin antagonists stimulate renin secretion and inhibit renin synthesis in vitro.

To find out whether calmodulin activity could be a common denominator for the cellular control of renin secretion and synthesis, we have examined the effects of calmodulin antagonists on the secretion and the synthesis of renin in primary cultures of mouse juxtaglomerular (JG) cells. We found that the calmodulin antagonists calmidazolium (CMDZ), N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide (W-7), and trifluoperazine (TFP) strongly stimulated renin release from isolated JG cells with a rank order of potency CMDZ greater than TFP greater than W-7. With the same order of potency as on renin secretion, CMDZ, TFP, and W-7 also inhibited de novo synthesis of renin. This decrease of renin synthesis went in parallel with a general inhibition of protein synthesis in the cultured JG cells. A comparable inhibition of total protein synthesis and renin synthesis as with CMDZ was achieved with cycloheximide. Cycloheximide, however, did not alter renin secretion within 20 h of incubation. Taken together, our findings suggest that inhibition of calmodulin activity exerts a powerful stimulatory effect on the exocytosis of renin in renal JG cells. Calmodulin activity on the other hand is also essentially required for protein and renin synthesis in JG cells. It is not very likely therefore that calmodulin activity positively links renin synthesis and renin secretion in JG cells.

Animals↗
PubMed1992

Coexpression of renin, angiotensinogen, and their messenger ribonucleic acids in adrenal tissues.

The presence of the two components of the renin-angiotensin system (RAS) has been systematically investigated in human normal and pathological adrenal tissues with two aims: 1) the detection of renin and especially angiotensinogen, which has not been reported before; and 2) to study possible differences in the coexpression of renin and angiotensinogen in tissue of cortical and medullary origin. The relative levels of renin and angiotensinogen mRNAs were determined by Northern blot analysis in normal (n = 5) and pathological adrenal tissues of cortical (n = 23) and medullary (n = 10) origin. Renin, prorenin, and angiotensinogen levels were also measured. Renin concentrations in normal and pathological adrenals were around 30-fold higher than those in the plasma of normal subjects, except for a Cushing's adenoma, which contains an extremely high renin content. Renin accounted for 56% of the total renin in normal adrenals and up to 87% in neoplastic tissues. This high proportion of renin indicates a likely conversion of prorenin to renin within these tissues. Renin mRNA was detected in each group of adrenal tissues. There was a significant correlation between the concentration of renin and its mRNA (r = 0.75; P less than 0.05). Angiotensinogen and its mRNA were detected in all normal and pathological adrenals. Compared to normal adrenal tissues, the relative amount of angiotensinogen mRNA was significantly higher in pheochromocytomas. However, the increased mRNA level in these tissues was not accompanied by a parallel increase in tissue angiotensinogen levels. Since the translational efficiency of angiotensinogen was verified by in vitro cell-free translation, the low level of angiotensinogen compared to the relatively high amount of its mRNA suggests a lack of storage of this protein in adrenal cells, as in liver cells. This study demonstrates that renin and angiotensinogen are coexpressed in normal and pathological tissues. Tissues of different cellular origin (zona glomerulosa, fasciculata, and medullary tissue), were able to express, store, and process renin and synthesize angiotensinogen. There was no obvious relationship between the expression of these proteins and the pathophysiology of the adrenal gland.

Adrenal Gland Diseases↗
PubMed1991

Monoclonal antibodies against a human juxtaglomerular epithelioid granular cell tumour.

With the exception of the renin-angiotensin system, the molecular composition of juxtaglomerular epithelioid granular cells (JEG cells) is unknown. We demonstrate the molecular peculiarities of these modified smooth muscle cells using monoclonal antibodies produced against a benign human JEG-cell tumour. Six out of 29 different clones produced antibodies that label JEG cells nearly exclusively. Antibodies from the other clones recognize JEG cells but also granularly or homogeneously distributed antigens of proximal tubule cells. This suggests antigenic similarity between granules of JEG cells and lysosomes of proximal tubule cells. Other clones produce antibodies which tag different cytoplasmic membranes or even mast cells. The antibodies directed exclusively against JEG cells promise to be useful tools to study their physiology and pathology.

Animals↗
PubMed1991

[Obstruction of pulmonary arteries. Contribution of the scanner and MRI. Apropos of 10 cases].

We present a retrospective study of ten patients presenting non specific clinical manifestations in whom the diagnosis of pulmonary embolism was documented by CT scan and/or MRI. Results of CT scan and/or MRI were compared to DSA bi-selective pulmonary angiography findings. In a large number of cases, CT scan and MRI allowed the detection of the obstruction within the right and left pulmonary arteries (RPA and LPA). Although these techniques did not permit the diagnosis of peripheral clots, pulmonary infarcts were usually depicted by these two procedures. CT scan and/or MRI could be performed as first-line investigations in case of atypical clinical symptoms because of their high relevance for proximal pulmonary artery obstruction, although these two non-invasive procedures cannot indicate the aetiology of the obstruction etiology.

Evaluation Studies as Topic↗
PubMed1990

[Perforation of a loop of the small intestine by a Kim-Ray Greenfield endocaval filter. Report of a case].

Kim-Ray filter complications are usually benign, such as angulation or slight migration. We report and compare with the literature one case of vena cava perforation associated with a small bowel lesion. The follow-up with regular abdominal plain X-rays allows detection of filter angulation, the first step before vena cava perforation. Cavography or CT scan depicts this perforation. Complete or partial surgical removal of the filter may be necessary.

Adult↗