Autoradiographic Distribution of Radioactive Sodium in Rat Kidney

A utoradiographs of kidney sections from rats injected with sodium 22 showed two areas of relatively high concentration of the radioisotope. The first area appeared in the outer medulla; the second appeared as an area of increasing concentration toward the papilla. Autoradiographs of sections labeled with chloride-36 appeared essentially the same. Autoradiographs of sections labeled with inulin-C(14)OOH showed an increased concentration in the inner medulla. These results may have a bearing on the counter-current multiplier hypothesis for the production of concentrated urine.

Blood Flow in the Human Calf during Tobacco Smoking

Blood flow in the human calf during cigarette smoking was measured by two methods. One technic, the disappearance rate of a radioisotope injected into a muscle, was used to indicate muscle capillary blood flow, while the other method, plethysmography, was used to measure the total blood flow of the calf including both skin and muscle. The smoking of 2 unfiltered, regular-size cigarettes produced a significant increase in muscle capillary blood flow in 14 of 17 normal subjects while plethysmographic blood flow changes were variable and not significant. Tests were performed to demonstrate that the increased muscle blood flow was not secondary to inhalation, that it was reproducible, and that the sympathetic nervous system probably was not involved. Intravenous nicotine produced significant increases in both muscle capillary and total calf blood flow. Patients with arteriosclerosis obliterans showed no change in muscle capillary blood flow during smoking.

Sodium fluxes in isolated frog brain

The properties of a preparation of isolated frog brain bathed in a Ringer's solution have been examined in order to determine whether it is suitable for study of ion movements. The preparation can be maintained in a steady state with respect to Na and water content for up to 5 hr. Under our conditions the washout of Na24 from preloaded brains appears to be made up of two components, a fast one having a half time of 7.4 min and a slow one having a half time of 54.6 min. The slow component of washout was affected by ouabain, iodoacetate, and cyanide and by reduced temperature, and appears to represent a cellular compartment. The fast component was not affected by metabolic poisons and appears to represent an extracellular space making up approximately 24% of the wet weight of the tissue. The effective diffusion coefficient of Na in this space was found to be 0.82 x 10–5 cm2/sec. A method of calculating Na fluxes from the data on Na24 washout is discussed.

Simultaneous assay of K42, Na24, and Br82 in body composition measurements

Simultaneous measurements of Na24 and K42 specific activities may be based on chemical, physical, or metabolic differences between these two radioisotopes. This paper describes a rapid and precise technique based on both physical and metabolic differences. Two counters, a gamma-ray and a beta-ray counter, are used. Two samples are collected from each patient at tracer equilibrium (40 hr after administration of K42, 50 μc; Na24, 30 μc; Br82, 20 μc): urine, which has a high chemical K: Na ratio, and serum, which has a low chemical K: Na ratio. The urine is counted in the beta-ray counter, which favors K42. The serum is counted in the gammaray counter, which favors Na24. To calculate the specific activities, equations are used which contain appropriate decay corrections, to permit calculation of the individual specific activities even though simultaneous counting of the samples in the two detectors is not required. The laboratory procedure is simple and straightforward, and the procedure gives results which are comparable in accuracy to methods which use only one isotope at a time. When counters of great sensitivity are employed, the procedure permits both small doses of radioisotope and long equilibration periods (40 hr). Total exchangeable chloride can be estimated at the same time by Br82 dilution. The calculation has been programed for a large digital computer.

radioisotope separation; total exchangeable sodium; total exchangeable chloride; total exchangeable potassium

Submitted on September 27, 1962