SUMMARY1. The method of sequential centrifugation has been used to obtain fluid samples from both the renal papilla and inner medulla of the rat.2. Experiments were carried out on Brattleboro rats with hereditary hypothalamic diabetes insipidus (DI; homozygous recessive), and on their (heterozygous) litter-mates with normal quantities of neurohypophysial vasopressin. Initial classification of the animals by measurement of urine volume and osmolality was confirmed by post-mortem bio-assay of the pituitary glands, in thirty-five out of forty-seven animals.3. In rats with DI, urine osmolalities comparable to those of heterozygous rats were obtained after four daily injections of 1 u. Pitressin Tannate in Oil (PTO). Under these conditions, when dehydration was superimposed for 72 hr, urine osmolality did not increase markedly. In heterozygous rats dehydrated for the same period of time, urine osmolality increased by some twofold.4. In rats with DI, the administration of PTO induced a rise of both sodium and urea concentrations in renal fluids and in urine. Dehydration during PTO administration caused a further rise of urea concentrations only. Dehydration per se significantly raised urinary and renal fluid urea concentrations, but sodium concentrations did not rise.5. In heterozygous rats dehydration per se increased both urea and sodium concentrations in renal fluids and urine.6. The evidence is discussed that the action of vasopressin involves factors apart from increasing the permeability of the distal nephron to water and urea. t M.R.C. Scholar.

The effect of the administration of vasopressin as subcutaneous Pitressin Tannate in oil (PTO) was studied in the Brattleboro rat. Rats with hereditary hypothalamic diabetes insipidus (DI), and rats heterozygous for this abnormality, were used. A minimum dose of 1000 mu. of PTO/24 h was necessary to restore the urinary volume and osmolality of DI rats to values comparable with those of heterozygous rats. The urinary excretion of antidiuretic activity in DI rats was shown to be related to the dose of PTO. Sodium and urea excretion, but not potassium excretion, were reduced by up to 50 % in the DI rat. No comparable changes were produced in the heterozygous rat. The possible mechanisms of these actions of vasopressin are discussed.

SUBSEQUENT to the observation that the intravenous infusion of fat emulsion caused a decrease in the nmyocardial oxygentension of dogs having anl experimentally produced nmyocardial infaretion, it was shown that the hyperlipemia following a large fat meal may precipitate an attack of angina pectoris in patients with severe coronary artery disease. 1-3 These attacks of angina developed about 5 hours after the fat meal, when lipeinia was near its peak. Although sublingual nitroglycerin gave subjective relief, the lipemia-induced angina could also be relieved by the intravenous injection of heparin. The plasma turbidity and triglyeeride level decreased followillg heparin, as expected, due to lipoprotein lipase activity.48 Therefore, it appeared that the level of lipemia had an effect upon the myocardium, i.e., anginal attacks developed at the time of hyperlipemia and were relieved by heparin, which induced "clearingo" of plasma. Since increasing the blood fat level in the dog decreased myoeardial oxygen tension, the present study was undertaken in order to determine whether the level of lipemia affects tissue oxygen tenision in man.The polarographic method of oxygen tension determination, which was used in the study of the dog niyocardium during fat infusion, is also a useful tool for investigation of oxygen tensioni in accessible tissue of man. It has been particularly adaptable to detern-iinations of skin oxygen tension, and thus used extensively in the study of peripheral Supported by a grant from the Lycomning County (Pennsylvania) Heart Association and the Heart Association of Southeasterni Pennsylvania.Presented in part at the Scientific Sessions of the American Heart Association, Philadelphia, Pa., October 25, 1959. Circulatzon, Volume XXII, November 1960 vascular disease. The limitations of the polaroraphic method, and the considerable information that has been obtained by its use, have been well summarized by Montgomery.9In preliminary experiments we had attempted to measure oxygen tension of the skin as lipemia developed following a fat meal. As might be expected, valid determinations of oxygen tension over the several hours of inereasing lipemia after fat ingestion were difficult to make. The polarographic method is most accurate when the subjects remain quiet, the electrode position is not disturbed, and the experiment is brief enough so that the slight downward " drift " of readings which always occurs when electrodes are in place for long periods will not hamper interpretation of data. The following procedure was therefore adopted in which oxygen tension determinations were made over reasonably brief periods during which plasma turbidity either remained at a constant level or decreased after heparin administration.

1. The isolated renal papillae of a rat were centrifuged in a two tube assembly which allowed fluid from the tissue to separate into the lower tube.2. The papillae were centrifuged for 15 min at 300 g and 1500 g consecutively.3. After intraperitoneal injection of Na 131I‐diatrizoate, the activities of urine, and fluid samples obtained from the papilla, were compared. It was found at 1500 g that the median value for papillary fluid activity was 1·52% of the activity of urine. This is evidence that the papillary fluid was virtually free from any contamination from the terminal collecting ducts.4. It is considered that the fluid sample obtained from the papillae by centrifugation at 1500 g is a representative and reproducible sample of interstitial fluid.5. The method was used to demonstrate changes in solute concentrations in the renal papillary fluid, following dehydration of rats.

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