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By means of direct arterial perfusion of the adrenal glands in the dog it has been shown that synthetic lysine vasopressin stimulates the secretion of hydrocortisone. This effect is not mediated via the adenohypophysis or any other organ but is rather the result of direct stimulation of the adrenal cortex by vasopressin itself.

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It has been postulated recently that renal bicarbonate reabsorption is entirely dependent on the exchange of hydrogen ions, derived from the dissociation of carbonic acid within the cells of the renal tubule, for the fixed base of filtered bicarbonate in the tubular urine (1-3). According to this theory, an elevation of the CO2 tension of the extracellular fluid results in an increase in the rate of bicarbonate reabsorption because it leads to an increase in the rate of hydrogen ion secretion.Earlier studies, however, indicate that chloride reabsorption may interfere with bicarbonate reabsorption presumably because of competition between these two ions for some common transport mechanism in the proximal tubule (4). Since plasma pCO2 was apparently within normal range in those experiments, it was thought of interest to study the effect of hyperchloremia on bicarbonate reabsorption in the presence of an elevated extracellular pCO2.Our results indicate that under these circumstances the rate of bicarbonate reabsorption does not depend entirely on the CO2 tension, but may, in part, depend upon the rate of chloride ion reabsorption. METHODSNormal adult mongrel female dogs were anesthetized by the intravenous administration of 0.46 to 0.62 mg. of sodium pentobarbital per kilogram of body weight. The trachea was cannulated with a "Y"-shaped glass tube, the two free arms of which served as inspiratory and expiratory airways by means of flutter valves. The animals breathed spontaneously throughout the entire experiment. The abdomen was opened by a midline in-1 Supported by grants-in-aid from the New York Heart Association and the American Heart Association.2Fellow of the New York Heart Association.3 Frances H. Zabriskie Fellow, St. Luke's Hospital.cision and each ureter cannulated with a polyethylene tube. The abdomen was then closed by a continuous silk suture and the polyethylene tubes brought through the suture line, care being taken not to kink the ureters and tubes. Urine was collected directly under mineral oil contained in a graduated cylinder.During the successive periods of study, the dog breathed first room air, then a mixture of CO, and air containing 10 per cent of CO,,The different solutions were administered at desired rates by means of a constant-speed Bowman pump via a cannulated brachial vein. As the operative procedure was begun, the animal was given intravenously within a 5 to 24-minute period 400 ml. of a 0.15 molar sodium bicarbonate solution containing 0.375 Gram per cent of creatinine. Then a sustaining infusion containing from 0.93 Gram per cent of NaHCO, to 1.175 Gram per cent of NaHCO, (0.11 to 0.14 molar solution) was administered at rates varying between 6.4 and 18.5 ml. per minute. This infusion also contained an amount of creatinine such that the dog received 15 mgm. of creatinine per minute. When the operative procedures were completed, a fifteen to thirty-minute equilibration period was allowed. Then control determinations were made, the animal breathing room air and receiving the sustaini...

In the anesthetized dog the pCO2 of the urine, arterial blood, and renal venous blood was measured before and after the intravenous administration of Diamox (acetazoleamide). The pCO2 of the urine always rose to a much greater degree than did the pCO2 of the arterial or renal venous blood This rise in urinary pCO2 could be explained satisfactorily neither by a rise in intracellular pCO2 nor by an increase in the rate of urine flow, but seemed best explained by the fact that Diamox itself acted as a urinary buffer.