Red blood cell volume and distribution after bleed-out in the rat as determined by Cr51-labeled red blood cells

A method to assess 59Fe in residual tissue blood content in mice and its use to correct 59Fe-distribution kinetics accordingly

BACKGROUND

Dysregulation of body iron-distribution may induce oxidative damage. To investigate the molecular mechanisms of iron homeostasis, corresponding essential genes are manipulated by many working groups. This asks for a simple method to pursue the resulting impact on body iron-distribution in mice.

AIM

To develop a method for the assessment of (59)Fe in residual tissue blood content and to correct this influence in (59)Fe body distribution studies.

METHODS

Iron status in male adult C57BL6 mice was adjusted by feeding diets with different iron content. Fractional contribution of organs to total body weight was determined after dissection. (59)Fe-labelled blood was injected in recipient mice to estimate total blood volume and residual blood content in all organs and tissues. The main experiment used these data to correct total (59)Fe tissue content at six intervals after (59)Fe injection (12h-28 days).

RESULTS AND DISCUSSION

The sum of (59)Fe in all organs was the same as determined in each mouse before dissection. (59)Fe in whole blood remained constant from the 4th day after injection on, and was highest in iron-deficiency. As in other species, residual blood content was highest in spleen and lungs. Nevertheless, (59)Fe in the iron-deficient spleen decreased to zero and intestinal (59)Fe-content also decreased significantly over time after correction for (59)Fe in residual blood. These findings suggest correct assessment of compartment sizes and (59)Fe in residual blood in each organ.

CONCLUSIONS

Differences in (59)Fe-distribution between iron status reflected changes in the expression of proteins of iron-transport and its regulation correctly. Thus, the method seems suitable to analyse body iron-distribution in consequence to genetic manipulations of murine iron homeostasis which is a prerequisite to assess possible toxicological consequences of iron supplementation.

Determination of residual erythrocytes in rat tissue homogenates using commercially available anti-red blood cell sera

A method to determine the residual erythrocyte content in rat tissue homogenates by means of radial immunodiffusion (Mancini et al., 1965) is described. The method makes use of commercially available antisera against rat erythrocytes. Tissues were homogenized after addition of digitonin and applied on Mancini plates. To measure within the linear part of the calibration curve, the tissue homogenates were diluted to concentrations between 0.062% and 2.5% wet weight content, depending on the type of tissue and on the degree of bleeding before the death of the animal. Recovery data of added blood as well as a comparison with results from organ distribution studies with 59Fe-labeled erythrocytes demonstrated that this simple method is sufficiently reliable and sensitive. The present procedure is to control experiments in which drug tissue levels (e.g., antibiotics) are to be determined and in which the drug content of residual blood is likely to bias the results to an unknown extent. It can be used as well in organ distribution studies of substances with a high affinity for erythrocytes (e.g., Pb; As in rats). It is possible to individually control the success of procedures without the use of isotopes--such as exsanguination or vascular perfusion--that are performed in order to reduce the blood content in the organs under consideration.

Elimination pattern and tissue distribution of intravenous iron-poly (sorbitol-gluconic acid) complex in the rat

The elimination pattern and tissue distribution in rats of intravenous [14C-gluconic acid]-poly(sorbitol-gluconic acid) and 59Fe-iron-poly(sorbitol-gluconic acid) complex, glusoferron (Ferastral) have been examined. Twenty-four hours after injection of 20 or 200 mg/kg of [14C-gluconic acid]-poly(sorbitol-gluconic acid), 5%-6% of the injected dose of radiolabel was eliminated as 14CO2 and about 85% in the urine and faeces. Administration of 59Fe-iron-poly(sorbitol-gluconic acid) complex (10 and 100 mg of iron/kg) resulted in a urinary and faecal excretion of about 18% and 40% of the given dose, respectively, during the first 4 days. Biliary excretion was low. The mean molecular weight of the biliary product after the iron complex was lower than that of the parent compound. Radiocarbon in tissues after 24 hours was negligible. Liver and bones accounted for most of the retained radioiron following 100 mg of iron/kg bodyweight of the 59Fe-iron complex with maximum levels of 27% and 12% of the injected dose, respectively, 4 days after dosing. Red cell incorporation of 59Fe attained a level of 16% at the end of 28 days.

Nonliner tissue disposition: salicylic acid in rat brain

A model was developed to detect nonlinear disposition of a drug in a tissue. The model was experimentally tested relating to salicylic acid disposition in the brain. Experimental data obtained in rats are reported for doses of 25 and 40 mg/kg ip. The parameters measured for each dose were the ratio of the area under the brain concentration-time curve to the area under the plasma concentration-time curve and the ratio of the maximum brain concentration of salicylic acid to the plasma concentration at that point in time. The ratios increased with dose; furthermore, ratios calculated using plasma concentrations corrected for plasma protein binding were dose dependent. Calculations performed on literature data for salicylic acid disposition in mouse brain corroborated the results of this sutdy. The existence of a saturable transport system for the elimination of salicylic acid from the brain is supported by the data presented. The rationale necessary to apply the model to any tissue is discussed.