Alan L. Orvis

Effect of Thiazide Diuretics on Plasma Volume, Body Electrolytes, and Excretion of Aldosterone in Hypertension

A study has been made at the Mayo Clinic of the results of treatment in 28 hypertensive patients receiving thiazide diuretics. The use of these agents produced a significant but very temporary reduction in plasma volume in most patients. The plasma volume reverted to or toward normal after the first week of treatment; therefore, hypovolemia could not explain the prolonged hypotensive effect of these drugs. Administration of thiazide diuretics did not deplete the body of its sodium stores, as measured by isotope studies in five patients on an unrestricted diet. Therapy with thiazides did not produce a persistent increase in urinary aldosterone excretion in the nine patients studied for this possibility.

Myocardial sodium extraction at varied coronary flows in the dog. Estimation of capillary permeability of residue and outflow detection.

Sudden injections of boluses containing both 131I-albumin and 24NaCl were made into the coronary artery inflow of isolated blood-perfused dog hearts. Indicator dilution curves were recorded using gamma emissions from both the intact heart and the coronary sinus outflow, with plasma flows, Fs, ranging from 0.3 to 1.8 ml/g min−1 Three measures of sodium extraction, E, during transcapillary passage were obtained from each site by comparison of the sodium and albumin curves. The most useful estimates of E were “instantaneous extractions” obtained from the later part of the upslope and the peak of the venous dilution curves (coronary sinus) or from the corresponding early phase of washout of the externally monitored curves (intact organ). Extractions were lower at higher flows. Permeability-surface area products, PS, were computed (1) by the formula PS = -Fsloge(1 - E), (2) by fitting the observed dilution curves with a Krogh capillary tissue cylinder model, and (3) by the approximating formula PS= -Fs loge (1- 1.14E). The two latter approaches provided a correction for back diffusion of tracer from tissue to blood. For sodium, the values of PS averaged 0.88 ± 0.36 (SD) ml/g min−1, (N = 52). At high flows, with Fs > 1.0 ml/g min−1, the values of PS averaged 1.01 ± 0.38 ml/g min−1(N = 11). Assuming S = 500 cm2/g and plasma to be 93% water, our findings suggest capillary permeabilities for sodium of about 3.1 x 10−5 cm/sec.

A simplified method of estimating renal function with iodohippurate I131

Summary Simultaneous PAH and single injection iodohippurate I 131 clearances were performed 23 times on 14 dogs. Excretion of the radioactive material was evaluated in two ways: (1) the I 131 per ml. of plasma, collected 60 minutes after the injection of iodohippurate I 131 , was related to the dose to give an “index of remaining activity,” and (2) the slope of disappearing plasmatic radioactivity between 40 and 60 minutes after injection was multiplied by the apparent volume of distribution of the dose to yield an iodohippurate disappearance value expressed in millimeters per minute. Results by the former method agreed well with PAH clearances (correlation coefficient 0.89), but results were even better by the latter technique (correlation coefficient 0.94). The disappearance of iodohippurate I 131 agrees well with the effective renal plasma flow in the dog.

Thorotrast-induced hepatoma presenting as hyperparathyroidism

Clinical findings mimicking primary hyperparathyroidism were present in a patient with hepatoma, which was diagnosed 27 years after administration of Thorotrast. External scintillation gamma‐ray spectrum analysis during life and autoradiographic studies after death demonstrated the presence of the radioactive contrast medium.

Rate of Disappearance of Cholesterol-C14 from the Bloodstream of Dogs.

Summary A simplified technic is offered for measuring plasma cholesterol-C14 after intravenous injection of this sterol; it consists of liquid scintillation counting of an alcohol-acetone extract of the plasma. The distribution of cholesterol-4-C14 in 2 normal dogs was calculated from a 60- to 70-day study of plasmatic radioactivity, assuming a 4-compartment mammillary system. Excretory rate constants of 1.5 and 1.6% per day of the retained dose were derived. Preliminary estimates of the “exchangeable cholesterol pool” were made. The size of this pool appeared to increase as serum cholesterol rose, either as the result of a high fat diet or of thyroidectomy.

A Compartmental Analysis of Single Intravenously Administered Doses of Tritiated Digoxin in Dogs.

Excerpt Tritiated digoxin was injected into dogs to study degradation of the glycoside and rates of distribution and excretion. In four dogs with biliary fistula, an average of 72.5 per cent of an ...