Tracer kinetics analysis of the extracellular spaces in saline perfused hearts.

BACKGROUND: Precise estimation of the cellular water content presupposes a correct definition of the water fraction in tissue extracellular space. Low molecular weight markers (LMM), such as sulphate ion and sucrose, are widely used to define extracellular space size despite indications that they penetrate the cell. In contrast, inulin, with molecular weight of about 5000, is commonly regarded as a cell impermeable extracellular marker. OBJECTIVES: To compare LMM with inulin as markers in determining extracellular space size. ANIMALS AND METHODS: The size of extracellular space in guinea pig hearts perfused with crystalloid solution (hydrated hearts) was determined morphometrically and by mathematical model analysis of washout kinetics of LMM ((35)SO(4), (14)C-sucrose) or (3)H-inulin. RESULTS: Morphometrically, the sizes of vascular and interstitial spaces in the hydrated hearts were estimated to be 102+/-8 mL/kg wet mass (wm) and 452+/-17 mL/kg wm, respectively. Comparable data were obtained from model simulation of tracer washout: 67 mL/kg wm for vascular space and 439 to 462 mL/kg wm for interstitial space. Tracer penetration into cellular water, as shown by model analysis, was 28% for LMM and, reported here for the first time, 18% for inulin. The observed edema was probably due entirely to fluid accumulation in the interstitial space. CONCLUSION: Intracellular penetration of LMM must be taken into account, especially in modern nuclear magnetic resonance spectroscopic methods of cellular water monitoring in isolated perfused hearts.

[The systemic and regional hemodynamics of laboratory rats and wild muskrats during diving]. / Sistemnaia i regionarnaia gemodinamika u laboratornykh krys i dikikh ondatr pri nyrianii.

1-min forceful immersion in water increased mean arterial pressure by 24% in Ondatra, decreased their heart rate by 71% and cardiac output by 36% Respective figures in Wistar rats were as follows: 19%, 62%, and 46% decrease. By the 50th sec of immersion cerebral blood flow increased 13-fold in Ondatra and 6-fold in Wistar rats.

Endotoxin reduces specific pulmonary uptake of radiolabeled monoclonal antibody to angiotensin-converting enzyme.

The biodistribution of radiolabeled monoclonal antibody (Mab) to angiotensin-converting enzyme (ACE) was examined in normal and endotoxin-treated rats. Endotoxin administration at a dose of 4 mg/kg induced mild or middle pulmonary edema. The ACE activity in lung homogenate remained virtually unchanged, while the activity of serum ACE increased 15 hr after endotoxin infusion. In normal rats, anti-ACE Mab accumulates specifically in the lung after i.v. injection. Endotoxin injection induces reduction of specific pulmonary uptake of this antibody. Even in non-edematous endotoxemia, the accumulation of anti-ACE Mab antibody (Mab 9B9) decreased from 19.02 to 11.91% of ID/g of tissue without any change in accumulation of control nonspecific IgG. The antibody distribution in other organs and its blood level were almost the same as in the control. In a case of endotoxemia accompanied by increased microvascular permeability, the lung accumulation of Mab 9B9 was reduced to 9.17% of ID/g of tissue, while the accumulation of nonspecific IgG increased to 1.44% versus 0.89% in the control.

[Systemic and regional hemodynamics in conscious rats during 24-hour antiorthostatic posture]. / Sistemnaia i regionarnaia gemodinamika u bodrstvuiushchikh krys v usloviiakh 24-chasovogo antiortostaza.

The systemic and regional hemodynamics during antiorthostatic hypokinesia were studied in male Wistar rats using the radioactive microsphere technique. The animals were hanged up by the tail with the head tilted down (30 degrees) and were able to exercise using only front limbs. Twenty four hours long exposure to antiorthostasis induced significant changes in systemic hemodynamics as well as in regional blood flow in skeletal muscles, spleen, liver and pancreas. Antiorthostasis induced blood flow changes in lungs, heart and brain were less pronounced.

[Hemodynamics in waking rats undergoing testicular exposure to elevated temperature]. / Gemodinamika u bodrstvuiushchikh krys pri vozdeistvii povyshennoi temperatury na semenniki.

Changes of systemic and regional hemodynamic parameters of the rat during heating of the lower part of the body in 41 degrees C water and after removing of the testis from abdominal cavity, were measured with labeled microsphere technique. Experimental cryptorchism reduced the blood pressure due to a decrease in total peripheral resistance. Hyperthermia of the testis increased the heart rate. Heating of the scrotal region led to an increase in the blood flow that did not, however, reach the value of the blood flow in testis of the control unrestrained rats, thus suggesting an inadequate blood supply of the testis during heating. The inadequate blood supply of the testis under hyperthermia may be one of the factors leading to lesions of the testis.

[Hemodynamic correlates of immobilization stress in the rat]. / Gemodinamicheskie korreliaty immobilizatsionnogo stressa u krys.

Changes of the systemic and regional hemodynamics were studied in alert Wistar rats during their immobilization. Cardiac output and regional blood flows were measured with microsphere technique. The stress evoked 12% blood pressure increase, 30% cardiac output increase and 10% total peripheral vascular resistance decrease. Blood flow was increased in skeletal muscles, in the heart and adrenal glands, whereas in the kidney and small intestine blood flow decreased.

[Nature of the hyperpotassic composition of the medium surrounding individual tissue mechanoreceptors]. / O prirode giperkalievogo sostava sredy, okruzhaiushchei odinochnye tkanevye mekhanoretseptory.

The ouabain effect on potassium concentration in the Pacini corpuscle fluid was studied using continuous perfusion of cat's mesenteric receptors with ouabain in Ringer's bicarbonate solution. To check the solution penetration into the corpuscles, Na36Cl and (G-3H)-ouabain were used. 2 . 10(-2) mM ouabain reduced (K+) in corpuscle fluid. The high potassium concentration in Pacini corpuscle fluid seems to be due to Na+--K+-ATPase system.