PubMed Health⌕ Search

Biomedical subjects

B Piryova

Publications and source records attributed to B Piryova.

15 recordsLinked to original sources
PubMed1995

Effect of lesions to the supramammillary area of the posterior hypothalamus on atrial natriuretic peptide release following acute blood volume expansion in conscious Wistar rats.

Acute blood volume expansion (AVE) is a potent stimulus for atrial natriuretic peptide (ANP) release. Since several central nervous structures are well known for their involvement in the regulation of fluid and electrolyte homeostasis and in the secretion of central ANP, we carried our experiments on 33 conscious Wistar rats in order to determine if the integrity of the supramammillary (SMA) hypothalamic area is essential for the peripheral ANP response to AVE. We performed stereotaxic electrolytic lesions of SMA in part of the animals. To obtain AVE we administered 2 mL saline/100 g b.m. for 2 minutes into v. jugularis through the chronically implanted venous catheters. Plasma ANP was assayed radioimmunologically. AVE significantly increased plasma ANP both in the intact animals and in the lesioned rats. This concluded that SMA is not involved in the regulation of peripheral ANP release during AVE.

Animals↗
PubMed1994

Effect of dopamine receptor blockade on the renal excretory response to acute volume expansion (AVE) in conscious Brattleboro rats.

UNLABELLED: All the studies were performed on chronically cannulated, conscious Brattleboro rats, housed in metabolic cages under standard conditions. The renal excretory indices: diuresis (V), sodium (UNa.V), potassium (UK.V), chloride (UCl.V) and osmotic (Uosm.V) excretion were measured under the following experimental protocol: (1) controls, (2) 2% volume expansion (AVE)-0.9% NaCl i.v. for 2 min, (3) Dopamine (DA) receptor antagonist Flupentixol (FLU) 0.5 mg.kg-1 i.v., and (4) AVE 10 min after i.v. application of FLU. All the indices studied, given as cumulative curves, showed a firm linearity with time during the whole experimental period (5 h) in groups 1 and 2 (p < 0.05), while such a relationship was not found significantly in groups 3 and 4. AVE quickly, strongly and significantly (p < 0.01) increased V and especially UNa.V, UCl.V and Uosm.V. Pretreatment with FLU potently suppressed the effect of AVE on the renal excretion. FLU alone decreased almost equally V and saliuresis. IN CONCLUSION: the DA antagonist FLU blocks the diuretic and saliuretic response to AVE probably by affecting tubular processes.

Animals↗
PubMed1991

Renal excretory function, atrial natriuretic peptide (ANP) and plasma renin activity (PRA) during long-term sodium loading in rats.

The effect of chronic sodium loading on the level of plasma atrial natriuretic peptide (ANP) and on plasma renin activity (PRA), as well as on the renal excretory function was studied. Fifty-six standardly bred Long Evans rats were divided into three experimental groups: controls, rats drinking 170 mmol NaCl/l solution instead of water, and rats consuming food with high sodium content (850 mmol NaCl/kg) for 21 days. During the study, we measured the amount of fluid intake, the parameters of the renal function: diuresis (VU); sodium, potassium and cloride excretion (UNa V, UKV and UClV), and the dynamics of body mass. On the 21st day the animals were sacrificed by decapitation. Plasma ANP and PRA were determined radioimmunologically. Packed cells volume and plasma Na and Cl concentrations were measured. The data showed a full compensation in sodium balance: the body mass dynamics in the three groups was similar; no changes in packed cells volume and plasma electrolytes were seen; UNaV and UClV were significantly increased in the groups with high sodium intake. PRA was significantly depressed in the two groups while ANP did not show any real changes. We concluded that it is PRA and not ANP that might participate in the regulation of chronic sodium balance.

Animals↗
PubMed1989

Potentiation of the diuretic and natriuretic effect of furosemide by the calcium antagonist nifedipine.

The renal excretory function was studied in rats under control conditions, after treatment with nifedipine, with furosemide and combined treatment with nifedipine and furosemide. The experimental animals were investigated in metabolic cages. Spontaneously excreted urine was collected for 6 h (under control conditions and when nifedipine was applied) and for two hours in the experiments with furosemide treatment. The diuresis, the excretion of sodium, potassium, chlorine, creatinine and the total amount of osmotically active substances were studied. Blood samples were taken from the heart under nembutal anaesthesia. The clearances and the excretory fractions of the substances tested were determined. The glomerular filtration was determined by the clearance of the endogenous creatinine. The blood pressure in the tail artery was measured in control experiments. Increased diuresis was observed after treatment with nifedipine, without substantial changes in the sodium, chlorine, potassium and total osmotic excretion. When furosemide was applied after pretreatment with nifedipine, the diuresis was by 33 per cent higher than when only furosemide was applied (p less than 0.01), sodium excretion was by 40% higher (p less than 0.01) and that of chlorine--by 16.9% (p less than 0.01). Potassium excretion remained unchanged. The results of the excretory fractions and of the clearances of the substances studied support the evidence about potentiation of the natriuretic and chlorouretic effect of furosemide under the effect of nifedipine. The concentrating function of the kidney, determined through the clearance parameter Cosm/TcH2O manifested an additional limitation under the effect of nifedipine.

Animals↗
PubMed1986

Renin-angiotensin system and renal excretory function under conditions of hypovolemia and limited sodium intake.

The renal excretory function of rats was investigated under conditions of reduced extracellular fluid volume (ECV) obtained by peritoneal dialysis with isotonic glucose solution 10% of the body mass and using sodium-deficient diet (consisting of boiled rice) with intact renin-angiotensin system (RAS) and after angiotensin converting enzyme blockade by Captopril. The experiments were made on male Wistar rats placed in metabolic cages. The diuresis, the excretion of sodium, potassium, chlorine and osmotically active substances in spontaneously released urine were tested over a period of 6 hours. Captopril was administered with Alzet osmotic minipumps at 80 micrograms/h rate of infusion (in the experimental animals with peritoneal dialysis) and intraperitoneally 1 mg/kg (in the animals subjected to sodium-deficient diet). Blocking of the converting enzyme with Captopril was found to increase the diuresis, as well as the sodium and total osmotic excretion after peritoneal dialysis and under sodium-deficient regime. Blocking of RAS with Captopril reduced the adaptive possibilities of the organism in the cases of reduced ECV and sodium-deficient diet.

Animals↗
PubMed1985

Effect of furosemide upon extracellular fluid volume depletion and kidney denervation in rats.

The effect of the diuretic Furosemide (4 mg/kg) is tested on rats housed in metabolic, cages. The excretory function of the kidneys is studied over a 2-hour period after Furosemide administration, according to the following parameters: diuresis, glomerular filtration, excretion and excretory functions of sodium, potassium, chlorine and total osmotically active substances. Reduction of the volume of the extracellular fluid (ECF) is induced by intraperitoneal administration of 0.3 M glucose solution in amount equal to 10 per cent of the body mass. Comparative studies are carried out in animals with intact kidneys (IK) and with bilaterally denervated kidneys (DK). The decreased ECF volume is found to limit strongly the diuretic and saliuretic effect of Furosemide. In the experimental animals with DK, the reduced ECF volume reduced the diuretic and saliuretic effect of Furosemide to a considerably lesser extent. In euvolemic animals Furosemide has potentiated effect in the case of DK. The conclusion reached is that intact kidney innervation is necessary for the Na-retaining function of the kidneys in the case of depleted ECF volume.

Aldosterone↗
PubMed1978

Method and programme for compartment analysis of exogenously introduced indicator substance.

The concept of the compartment structure of body fluids gives possibilities for finding the values of physiological characteristics such as volume of distribution, transport rate, kidney and intercompartment clearance. Their determination is made indirectly and it is based on the solution of a system of differential equations describing the behaviour of an open two-compartment system when an indicator substance is introduced. The determination of the coefficients of the equations involves a number of difficulties leading to inaccurate results due to the use of graphic-analytical methods. It is proposed to avoid this shortcoming by applying multiple approximation of the function describing the change in time of the concentration of the indicator substance in the intravasal space by a sum of two exponents, which corresponds to the system of differential equations. The approximation is performed by the least squares method, the precision criterion being the mean quadratic error of the approximation. An algorithm for which a computer programme is elaborated is proposed.

Biological Transport↗