Morton F. Mason

Effects on Blood Pressure of Injection of Kidney Extracts of Dogs with Renal Hypertension

A rise in blood pressure may be produced in dogs either by partial obstruction of the renal arteries 1 or by ligation of the ureters. 2 Since the latter procedure often causes a marked decline in the renal blood flow, 3 it seems likely that the hypertension is in both instances related in some way to ischemia of the kidneys. It was shown by Tigerstedt and Bergman 4 that saline extracts of the kidney of rabbits produced a sustained rise in blood pressure when injected into other rabbits. The object of our experiments was to determine whether extracts prepared from ischemic kidneys, removed from dogs with hypertension, had a greater pressor effect than similar extracts of normal kidneys. The freshly removed kidneys were chopped up with scissors and ground with carborundum and 0.9% salt solution. The suspension so obtained was centrifuged and the supernatant fluid was kept in the ice box until used. Amounts corresponding to 5 gm. of kidney tissue were administered intravenously to normal unanesthetized dogs. Changes in blood pressure were measured by the cuff described by Ferris and Hynes, 5 the passage of the pulse wave being determined by palpation of the dorsal artery of the foot. 6 The results which have been obtained are summarized in Table I. Extracts of the normal kidneys frequently caused a marked preliminary decline in blood pressure, followed in a few minutes by a gradual rise which persisted for 30 minutes or longer. The degree of rise varied from zero to 60 mm. of mercury above the control values. Extracts of the kidneys of dogs with renal hypertension usually caused less preliminary decline and a more marked secondary rise in blood pressure.

Renal Oxygen Utilization of Dogs with Experimental Hypertension.

Summary The variability of renal arterio-venous oxygen difference in fasting dogs with partial constriction of the renal artery with and without hypertension is similar to that of normal dogs.

Attempts to Demonstrate Vasopressor Properties in the Serum of Hypertensive Dogs

Summary Particular pressor properties could not be demonstrated in serum of the renal venous blood of hypertensive dogs by use of the Läwen-Trendelenberg per fusion technic with bullfrogs, frogs, and toads as test objects.

A Note upon the Micro-Determination of Ammonia.

Several excellent procedures are available for the micro-estimation of ammonia of which the methods of Conway and Byrne 1 and Gibbs and Kirk 2 are notable examples. In connection with studies of tissue respiration it became desirable to determine quantities of ammonia of the order of 5 γ to 50 γ present in the Ringer fluid in which various tissues were suspended. Attempts were made to Nesslerize the de-proteinized fluid with measurement of the resulting light transmission with the Evelyn photoelectric colorimeter (Filter 440) as in the micro-non-protein nitrogen determination adapted for this instrument. 3 These were frustrated by immediate clouding of the Nessler-ized solutions as a result of the small amount of magnesium ion present in the Ringer fluid 4 employed. Inhibition of the precipitation was not obtained by addition of various stabilizers, e. g., gum ghatti, gum acacia, etc., although the onset and rate of clouding was slightly delayed by adding a small amount of 50% Rochelle salt solution prior to Nesslerization. This slight delay sufficed to make the photoelectric determination feasible. The following technic was found to yield moderately accurate results in spite of interfering magnesium salts.

Observations on the Locus of Deamination.

Conclusion The absence of a demonstrable arterio-renal venous difference in amino acid amino nitrogen at various intervals following feeding of meat to dogs indicates that the kidney does not play a quantatively important rôle in the deamination of absorbed amino acids in the normal intact animal.