Meyer Friedman

Observations concerning the metabolism of cholesterol in the hypo- and hyperthyroid rat.

The administration of thiouracil induced a rise and administration of thyroid substance a decrease of the plasma cholesterol concentration in rats. The concentration and daily output of bile cholesterol was markedly reduced in hypothyroid rats and markedly increased in hyperthyroid rats. Evidence is presented which suggests that the rate of synthesis of cholesterol is significantly increased in the hyperthyroid rat and decreased in the hypothyroid rat.

Depressor Effect of Potassium Restriction on Blood Pressure of the Rat

Summary (1) Dietary restriction of potassium was found to lead to the occurrence of hypotension in the rat. (2) This depressor effect of potassium deprivation was prevented by simultaneous dietary withdrawal of sodium.

Deposition and Disappearance of Digitoxin from the Tissues of the Rat, Rabbit, and Dog after Parenteral Injection

Digitoxin administered to the rat, rabbit, or dog has no specific avidity for heart muscle. The quantity recovered from this organ at any time was no greater than from liver or kidney, while these organs continued to contain the glycoside for a much longer period of time.

Studies Concerning the Site of Renin Formation in the Kidney. II. Absence of Renin in Glomerular Kidney of Marine Fish.

Summary The absence of renin in the aglomerular kidney of the midshipman, a marine fish, cannot now be construed as suggestive evidence of the probable formation of renin by the glomerular or arterial component of a kidney because the glomerular kidneys of other marine fish studied, also lack renin. The presence of renin in the glomerular kidneys of the catfish and carp, however, suggests that the kidney of most fresh water fish contains renin. Just why the kidney of marine fish, whether glomerular or aglomerular, should be devoid of detectable renin and the kidney of fresh water fish richly supplied with this same substance is a question which cannot be answered at this time. As has been noted, already, there is evidence that the tubular function in the kidneys of these two varieties of fish is probably not identical.

Effect of Potassium Administration on (1) Peripheral Vascular Reactivity and (2) Blood Pressure of the Potassium-Deficient Rat

One hour after administration of potassium chloride to potassium-deficient rats, the depressed peripheral vascular response to pressor substances was significantly elevated. Administration of potassium chloride to potassium-deficient rats also returned to higher levels the lowered blood pressure of previously normotensive, as well as hypertensive rats. It appears that the depressor effect of potassium deprivation is due to the loss of peripheral vascular reactivity, both of which are rapidly restored by potassium administration specifically.

The Deposition of Digitoxin in the Tissues of the Rat After Parenteral Injection

Quantitative studies regarding the fate of parenterally injected digitoxin in the rat were made by assaying extracts of rat tissue by the embryonic duck heart method. The concentration of digitoxin found in heart muscle was similar to that found in lung and kidney and greater than the concentration in skeletal muscle. The greatest amount was found in the liver and suggested the importance of this organ in the excretion or destruction of digitoxin.

The Renal Excretion of Digitoxin in the Normal Subject after Single and Continuous Administration of the Drug

By employing the embryonic duck heart method to assay digitoxin quantitatively in extracts of human urine, it was found that, contrary to previous opinion, a large percentage of ingested or in-injected digitoxin is excreted via the kidney in a physiologically active state. Approximately 40 per cent of a digitalizing dose (1.2 mg.) is excreted over a period of 12 to 24 days. The average rate of renal excretion in theoretically digitalized normal young individuals was found to vary from 30 to 50 &mgr;g. of digitoxin per day, while those showing signs or symptoms of overdosage excreted significantly greater amounts of digitoxin.

The Peripheral Vascular Reactivity of Potassium-Deficient Rats

Peripheral vascular reactivity was studied in the potassium-deficient and control rats by measuring the degree of blood pressure response to intravenously injected pressor substances. The pressor response consistently was less in the potassium-deficient rats. The significance of these results with regard to the hypotensive action of potassium deprivation is discussed.

THE CHANGES IN THE BLOOD PRESSURE AND IN THE RENAL BLOOD FLOW AND GLOMERULAR FILTRATION RATE OF HYPERTENSIVE PATIENTS FOLLOWING UNILATERAL NEPHRECTOMY

In 1937 Butler (1) reported two cases of hypertension associated with unilateral kidney disease in which the hypertension was apparently abolished by the removal of the affected kidney. Since that time, there have been numerous reports (2 to 6) concerning the blood pressure changes occurring after the extirpation of a single diseased kidney in hypertensive patients. Although marked reductions in blood pressure have been reported following this type of operation, it appears that in the majority of cases the blood pressure of these patients had not returned to a normotensive level after the extirpation of the affected kidney. Indeed, Schroeder and Fish (6) in an analysis of previously published reports and a study of their own patients came to the conclusion that the efficacy of this particular surgical measure was very limited. Wilson and Byrom (7) and Friedman, Jarman and Klemperer (8) also reported that in their experimental animals the resulting hypertension from unilateral kidney derangement did not entirely disappear when the affected kidney was removed. These observers were inclined to believe that the persistence of the hypertension in their animals was related to the organic changes in the arterioles of the remaining kidney, which occurred during the prior existence of hypertension. Since the hypertension present in individuals with unilateral kidney disease has been assumed to be due initially to this deranged kidney, it was thought advisable to study the renal hemodynamics in such hypertensive patients, both before and after the removal of the diseased kidney. In this communication, the results of such a study, together with the blood pressure changes following unilateral nephrectomy, are reported. METHODS

Employment of the Embryonic Duck Heart for the Detection of Minute Amounts of a Digitalis Glycoside (Lanatoside G)

Conclusion The embryonic duck heart, similar to the embryonic chick heart was found to exhibit sensitivity to the action of a digitalis glycoside as characterized by alteration in rate, rhythm and force of contraction. Moreover the embryonic duck heart was able to be used to detect as little as one two-hundredth of a microgram of the digitalis glycoside (Lanatoside C.) This is thought to represent the most sensitive indicator now available for the presence of a digitalis glycoside.