Biomedical subjects

L N Ivanova

Publications and source records attributed to L N Ivanova.

At least 19 recordsLinked to original sources

PubMed2006

Hydruric response in Wistar and vasopressin-deficient Brattleboro rats to water load under conditions of increased brain serotonin level.

The hydruric response to water load in Wistar rats and homozygous Brattleboro rats with a hereditary defect in the synthesis of vasopressin was studied under conditions of increased brain serotonin level. Serotonin prevented the reduction in reabsorption of osmotically free water in normal rats, but had no effect in vasopressin-deficient Brattleboro rats. Our results suggest that serotonin stimulates vasopressin secretion and interacts with the vasopressinergic system during the realization of osmotic regulation.

Animals↗

PubMed2006

[Developmental peculiarities of short-term nongenomic effect of aldosterone on intracellular sodium concentration in rat distal nephron].

Intracellular sodium concentration in CCD fragments micro-dissected from the kidneys of 10-day and adult rats using fluorescent dye Na+ Green, was studied. The steady state level of intracellular sodium was lower in fragments from amiloride kidney (24.50 +/- 1.3 and 35.3 +/- 4.9 mM, n = 8, respectively). Amiloride reduced this parameter but, in the epithelia cells from immature kidney, the effect of imaloride was less pronounced. Fast nongenomic action of aldosterone on intracellular sodium concentration was found in both groups. Aldosterone significantly raised the steady state sodium level in epithelial cells in conditions of low sodium concentration (14 mM) in outer medium in both type of CCD fragments: from 10-day pups and adult animals (4.0 +/- 1, 5.5 +/- 0.5 and 5.1 +/- 0.2, 7.9 +/- 0.2 mM, n = 8). We suggest that, along with the well-known mineral-corticoid effect, aldosterone takes part in regulation of cell volume in CCD rat kidney from the earliest stages of postnatal ontogenesis.

Aging↗

PubMed2006

[Calciumdependent mechanisms in vasopressin regulation of osmotic water permeability in the mouse kidney collecting duct cells].

In the study, the role of PKC and Ca++ in vasopressin regulation of the plasma membrane water permeability was studied in the cells of the mouse kidney collecting duct. Coefficient of osmotic water permeability of total cell surface (Pf) was calculated from the initial rate of cell swelling following the osmotic shock caused by changing the medium osmolarity from isotonic to hypotonic (300 mOsm to 200 mOsm). Desmopressin (dDAVP 1 nM) increased the Pf in hydrated mice from 168.4 +/- 11.8 microm/s up to 231.3 +/- 14.7 microm/s. The Ca++ chelator BAPTA prevented the desmopressin-induced increase in water permeability. Inhibition of PKC (Ro-31-8220 0.1 microM) also abolished the desmopressin-stimulated increase of plasma membrane water permeability, whereas inhibitor of PKC alone did not suppress the stimulation of the water permeability by db-cAMP. The PKC activity and calciumdependent second messengers seem to be important for regulation of water permeability by vasopressin.

Animals↗

PubMed2006

[Effect of vasopressin gene expression on the growth of Walker 256 carcinosarcoma in rats].

The growth pattern of the Walker 256 solid tumor has been studied in rats with different doses of the mutant vasopressin gene. In contrast to the vasopressin gene of normal WA rats, that of mutant Brattleboro rats has a deletion in the coding region that blocks expression at the translation level. The mutation is inherited as a recessive character and is expressed in homozygous Brattleboro rats as diabetes insipidus with an increased water consumption because of the absence of vasopressin in the blood. (WAG x Brattleboro) F1 hybrids have the same normal phenotype as WAG rats, including a low water consumption. Walker 256 carcinosarcoma, which is not strain-specific, intensely grows only in WAG and (WAG x Brattleboro) F1 rats. In these groups, the growth of the tumor leads to the animal death within approximately 30 days after the inoculation of tumor cells. In Brattleboro rats, the carcinosarcoma grows less intensely: the tumor node somewhat increases only within the first two weeks, after which the tumor began to decrease and eventually disappears altogether. Both characters exhibit a 100% concordance at the individual level.

Animals↗

PubMed2004

[Age-related specifics of aldosterone reception in distal segments of the rat nephrons and of Na(+), K(+)-ATPase expression induction].

The reason of unresponsiveness of young 10-day rats kidney to aldosterone was explored. The aldosterone binding in distal segments of renal nephrons and the influence of hormonal induction on the mRNA of the alpha and beta subunits of the Na+, K(+)-ATPase in 10-day and 2-month old rats were investigated. There was no age related difference in the aldosterone specific binding in presence of RU-38486 (10(-7) M; Russel Uclaf) in the cortical collecting tubules: 0.26 +/- 0.04 (n = 9) and 0.22 +/- 0.03 (n = 8) mMol/mm of tubule lengths in 10 day and adult rats, respectively. By Nozern blot analysis and RT-PCR more then three and two fold increase of the mRNA abundance of both subunits was found in young and adult renal cortex compare to the adrenalectomized control after aldosterone induction (5 micrograms/100 g. v. b. w. 4 times i/p injections in 3 hour interval between injections) (p < 0.01). By RT-PCR no expression of the alpha 2, alpha 3 and beta 2 isoforms has been observed in all experimental conditions. The age difference was discovered when aldosterone was injected together with spironolactone (5 micrograms and 12 mg per 100 g. b. w. respectively). It was shown, that spironolactone inhibits the effect of aldosterone in adults whereas the latter was unaffected in young rats. The scheme of the age-related differences in the aldosterone regulation of the sodium pump induction in the target cell of the distal part of the rat nephrons is presented.

Age Factors↗

PubMed2004

[Water permeability of the OMCD and IMCD cells' basolateral membrane under the conditions of dehydration and dDAVP action].

Water permeability of the basolateral membrane was estimated in isolated fragments of OMCD or IMCD in the Wistar rats. Apical surface of the fragments was blocked with oil injected into the lumen. Apparent water permeability coefficient (Pf) was measured by the rate of epithelium swelling following transition from hypertonic to isotonic medium (600 mOsm to 300 mOsm). Water deprivation caused significant increase in the Pf value in OMCD and IMCD fragments. Desmopressin (10(-8) M) increased water permeability in hydrated rats both in OMCD and IMCD. Mercury chloride decreased the Pf and abolished the effect of desmopressin in reversible manner. Estimation of aquaporins 2, 3, 4 mRNA content in the renal medulla was performed by semi-quantitative RT-PCR. Content of AQP4 and AQP2 mRNA in dehydrated animals was significantly higher than in hydrated ones both in outer medulla and inner medulla. Expression of AQP3 increased during dehydration only in the inner medulla. The findings reveal that water permeability of OMCD and IMCD can be increased by physiological stimuli, e.g. water deprivation. The activation of gene expression of the key elements of vasopressin signal system seems to contribute to this reaction.

Animals↗

PubMed2003

Effect of dDAVP on basolateral cell surface water permeability in the outer medullary collecting duct.

We report a novel approach for assessing the volume of living cells which allows quantitative, high-resolution characterization of dynamic changes in cell volume while retaining the cell functionality. The aim of this study was to evaluate the short-term effect of vasopressin on basolateral cell surface water permeability in the outer medullary collecting duct (OMCD). The permeability of the basolateral cell membrane was determined in the tubules where the apical membrane was blocked with oil injected into the lumen. The apparent coefficient of water permeability (Pf) was evaluated by measuring the cell swelling after the step from hypertonic to isotonic medium (600 mosm to 300 mosm). Desmopressin (dDAVP) induced an increase of the basolateral Pf from 113.7+/-8.5 microm/s in control cells to 186.6+/-11.4 mum/s in micro-dissected fragments of the OMCD incubated in vitro (10(-7) M dDAVP, 30 min at 37 degrees C) (P<0.05). Mercury caused pronounced inhibition of basolateral water permeability (26.0+/-6.9 microm/s; P<0.05). The effect of mercury (1.0 mM HgCl2) was reversible: after washing the fragments with PBS for 20 min, Pf values were restored to the control levels (125.0+/-9.5 microm/s). The results of the study indicate the existence of a mechanism controlling the osmotic water permeability of the basolateral cell membrane in the OMCD epithelium.

Animals↗

PubMed2003

Immune system in vasopressin-deficient rats during ontogeny.

Morphofunctional immune disorders were revealed in vasopressin-deficient Brattleboro rats with diabetes insipidus during ontogeny. We observed a permanent decrease in the number of blood lymphocytes, increase in neutrophil count, reduced activity of macrophages, early involution of the thymus and spleen, and suppression of antibody production. These changes reflect impaired general resistance of these animals.

Animals↗

PubMed2003

[Osmoregulating reactions following serotonin metabolism inhibition or activation].

Effect of p-chlorphenilalanine and 5-hydroxytriptophan on the urine flow (V), glomerular filtration rate (GFR), free water reabsorption (TCH2O), and sodium fraction excretion (ENa.F%) in Wistar rats loaded with water or 2% sodium chloride solution, was studied. It was found that treatment of rats with inhibitor of serotonin biosynthesis, p-chlorphenilalanine (300 mg/kg, 48 hrs before the experiment) had no effect on the kidney response to the water loading in the experimental rats as compared to the control ones: changes in V, GFR, TCH2O and ENa.F% were the same. Treatment of rats with precursor of serotonin, 5-hydroxytriptophan which is known to increase the serotonin level in the brain (50 mg/kg) simultaneously with the water loading prevented the development of the diuretic reaction because of the high level of TCH2O reflected in the blood vasopressin concentration. Injection of 5-hydroxytriptophan at the maximum level of water diuresis resulted in the sharp increase in TCH2O and drop of the V. 5-hydroxytriptophan had no significant effect on the kidney response to the loading with the 2% sodium chloride solution. Under these conditions, increase in V was produced by suppression of the distal tubular sodium reabsorption, the TCH2O remaining at the high level. It is suggested that the brain serotonin manifested a significant stimulating effect on the vasopressin release from the neurohypophysis, but it is not involved in the mechanisms of suppression of its release into the blood. Serotonin seems not to interact with brain mechanisms regulating natriuretic function of the kidney.

5-Hydroxytryptophan↗

PubMed2003

[Vasopressin-dependent water permeability of the basolateral membrane of the kidney outer medullary collecting duct in postnatal ontogenesis in rats].

Kidneys of new-born animals are resistant to arginine vasopressin (AVP). The ability of the hormone to regulate water permeability of the collecting duct can be seen from weaning period, probably due to the maturation of the intracellular signaling pathway. The purpose of the present work was to investigate the effect of V2 receptor agonist dDAVP on the water permeability of OMCD basolateral membrane in 10-, 22- and 60-day old Wistar rats. We also estimated ontogenetic gene expression of AQP2, AQP3, AQP4 and V2 receptor. Osmotic water permeability (Pf) of the basolateral membrane of microdissected OMCD was measured under control conditions and after incubation with the agonist V2 receptor desmopressin (dDAVP; 10(-7) M). Water permeability in 10- and 22-day old rats under control conditions were significantly higher than in adults. Desmopressin stimulated significant increase of this parameter in 22-day old pups (Pf = = 125 +/- 4.85; Pf = 174 +/- 8.2 microns/s, p < 0.001) and adult rats (Pf = 100.5 +/- 7.38; Pf = 178.8 +/- 9.54 microns/s, p < 0.001). Osmotic water permeability of the OMCD basolateral membrane in 10-day old rats does not depend on dDAVP (Pf = 172.5 +/- 23.8; Pf = 164.8 +/- 34 microns/s). With the RT-PCR, we observed a gradual increase of AQP2 and V2 receptor genes expression during postnatal ontogenesis. The gene expression of AQP3 and AQP4 remained unchanged during postnatal ontogenesis. In general, the water permeability of the OMCD basolateral membrane of rats can be stimulated by AVP since the 22nd day of postnatal life. The water permeability of the OMCD basolateral membrane under control conditions gradually decreased during postnatal development, while gene expression of AQP3 and AQP4 was unchanged. The mechanism of this decrease remains to be established.

Aging↗

PubMed2002

Hypothalamic tryptophan hydroxylase and the hypothalamic-pituitary-adrenocortical response to water deprivation and hydration in vasopressin-deficient and normal rats.

The effects of water deprivation and hydration on plasma corticosterone concentration and the activity of tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin (5-HT) biosynthesis, in the hypothalamus of vasopressin- (AVP-) deficient homozygous Brattleboro and normal Wistar rats were studied. In the Wistar rats, water deprivation caused an increase in the TPH activity in the anterior and middle (infundibular) parts of the hypothalamus, while hydration did not affect the activity of the enzyme in the anterior hypothalamus but produced an increase in its middle part. In contrast, in the Brattleboro rats, water deprivation had no effect on TPH activity in the anterior and middle parts of the hypothalamus but hydration produced a decrease in TPH activity in the anterior hypothalamus. After 48 h of water deprivation, the plasma corticosterone concentration significantly increased in water-deprived and decreased in hydrated Wistar rats. Under water deprivation, the rise in corticosterone concentration in the homozygous Brattleboro rats was significantly greater than that in the Wistar rats. The data provide evidence that the CRH-like activity of AVP is not necessary for activation of the hypothalamic-pituitary-adrenal system induced by water deprivation. The observations show that AVP is involved in the activation of TPH induced by water deprivation. This suggests that AVP modulates the metabolism of 5-HT and the response of the 5-HT-ergic system to water deprivation.

Animals↗

PubMed2002

[Effect of dehydration and dDAVP on water permeability of basolateral membranes of epithelial cells in the kidney collecting tubules].

Water permeability of the outer medullary collecting duct's (OMCD) basolateral membrane was determined in vitro in the tubules isolated from hyperhydrated or dehydrated Wistar rats. Oil was injected into the lumen to block apical membrane water permeability. OMCD fragments underwent a hypoosmic shock (600/300 mOsm) and epithelial cells volume increased ad recorded with a digital camera. The latter's rate was used to calculate apparent water permeability of the membrane (Pf). Treatment of the tubules with Hg2Cl2 suppressed the water permeability. Water deprivation and dDAVP induced an increase in the basolateral water permeability. The data obtained suggest that the water permeability of the OMCD basolateral membrane may be stimulated by vasopressin and water deprivation.

Animals↗

PubMed2001

Effects of vasopressin on hyaluronate hydrolase activities and water permeability in the frog urinary bladder.

The involvement of enzymes catabolizing hyaluronic acid (hyaluronidase, beta-glucuronidase, N-acetyl-beta-D-hexosaminidase) in the hydroosmotic effect of vasopressin in the frog (Rana ridibunda) urinary bladder was studied. It was observed that vasopressin (50 nM), an agonist of V2 receptors, L-desamino-8-D-arginine-vasopressin (dDAVP, 1.5 microM) and forskolin (30 microM) activated the enzymes and caused their release into Ringer solution at the mucosal side, together with an increase in osmotic water flow. The effect of AVP on enzyme activity developed 10 min after the hydroosmotic response. Cytochalasin B (a specific inhibitor of actin filament elongation, 50 nM) blocked the hydroosmotic response to AVP; hyaluronate hydrolase activity increased in the bladder tissue but not in Ringer solution. It is suggested that the involvement of hyaluronate hydrolases in AVP's effect is mediated by a cAMP-dependent mechanism and provides favorable conditions for an increase in the permeability of glycosaminoglycan structures adjacent to the apical cell surface.

Animals↗

PubMed2001

Role of various types of serotonin receptors in regulation of drinking behavior and salt appetite in vasopressin-deficient brattleboro rats.

Serotonin 5-HT(1A)receptor agonist 8-OH DPAT suppressed drinking behavior in Brattleboro and Wistar rats. 5-HT(1B)agonist CGS-12066A and 5-HT(2A)antagonist ketanserin did not affect drinking behavior in Brattleboro rats; 5-HT(3)antagonist ondansetron suppressed water consumption and 5-HT(1A)agonist stimulated salt appetite in Brattleboro, but not in Wistar rats. Presumably, vasopressin regulates thirst and salt appetite by modulating sensitivity/density of various types of 5-HT receptors.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed2001

[Participation of various types of serotonin receptors in the regulation of drinking behavior and salt appetite in rats].

The 5-HT1A agonist 8-OH-DPAT was shown to diminish the water and 1.8% NaCl solution consumption, whereas its antagonist pMPPI--to enhance the water intake in rats. Another agonist: CGS-12066A enhanced water intake or exerted no effect on drinking behaviour and diminished salt intake. Other substances under study exerted various effects. The data obtained suggest that the 5-HT receptors are involved in regulation of water and salt intake, even though the mechanisms of the effects are different. Apparently 5-HT1B and 5-HT2A receptors play an activating role in regulation of water intake, whereas 5-HT1A, 5-HT2C and 5-HT3 receptors act as inhibitory ones. Only three of the receptors under study seem to regulate salt intake by inhibiting the salt appetite.

Animals↗

PubMed2001

[Effect of vasopressin on water permeability of epithelial cells in the kidney collecting duct during postnatal ontogenesis in rats].

Desmopressin caused a statistically significant increase in the water permeability of the outer medullary collecting ducts (OMCD) in 22-days old rats. Concentration of specific V2 receptors increased during postnatal period. Comparison of the V2 receptors concentration, mRNA contents, and changes of water permeability in response to desmopressin suggests that parts of transduction mechanism is situated deeper than the receptors, determines the physiological mechanism at the end of weaning period.

Animals↗

PubMed2000

[Serotonin metabolism in the rat brain during water deprivation and hydration].

Water deprivation (WD) decreased the serotonin (5-HT) level and significantly increased the 5-hydroxyindoleacetic acid (5-HIAA) in the rat midbrain and hypothalamus, the catabolic 5-HIAA/5-HT ratio increasing three-fold. Hydration (H) produced a moderate increase in the 5-HT and 5-HIAA levels in the hypothalamus with no changes in the 5-HIAA/5-HT ratio. Hydration exerted no significant effect upon the 5-HT level and metabolism in the midbrain. A two-fold increase of corticosterone concentration in water deprivation and its decrease in hydration were shown to occur in peripheral blood plasma.

Animals↗

PubMed1999

[Vasopressin: cellular and molecular aspects of its antidiuretic effect].

The paper reviews current data on molecular mechanisms of action of the neuropituitary hormone vasopressin (VP) on the aqueous epithelial permeability of the amphibian renal tubules and urinary bladder. It considers the structure and function of VP receptors, cAMP-dependent cellular events induced by VP, the action of different modulators on the effects of VP, the structure and localization of proteins that water-forming channels within the cellular membranes along the renal tubules. The development of VP sensitivity in ontogenesis is shown to be associated with age-related changes in the membrane receptor complex and with the higher activity of the adenylate cyclase mechanism.

Adenylyl Cyclases↗