Fibrillation and potassium influx

Absolute influx and efflux of potassium-42 have been measured in isolated rabbit atria during acetylcholine-induced fibrillation. The efflux of potassium was increased three to four times; influx was not changed. The data are interpreted as indicating that an inhibition of active K uptake is not involved in the initiation of fibrillation, and that the process results from a marked increase in Na permeability.

Influence of the rate of coronary plasma flow on the extraction of Rb86 from coronary blood

To determine whether myocardial uptake of Rb 86 can be used as a useful index of coronary plasma flow, the extraction of Rb 86 from arterial plasma during one passage through the myocardium of dogs was measured at varying rates of flow. At rates of flow which are encountered in man, changes in the rates of flow and uptake of isotope by the myocardium paralleled each other closely. Rb 86 uptake is a useful index of coronary blood flow in dogs.

Effects of renal hypertension on coronary blood flow, cardiac oxygen consumption and related circulatory dynamics of the dog

A comparative study is presented on the circulatory dynamics of the renal hypertensive state, the stability (repeatability) of the findings in a given subject, the effect of anemia as a complicating factor and the amount of cardiac hypertrophy present in each animal at the end of the series of observations. The results indicate that in nonanemic renal hypertensive dogs with cardiac hypertrophy the coronary blood flow and cardiac oxygen consumption are the same per unit weight of myocardial tissue as in normal dogs. However, when a mild chronic anemia is a complicating factor, the coronary blood flow and the myocardial oxygen uptake are both increased. The coronary sinus venous oxygen saturation is essentially unchanged in the nonanemic hypertensives, whereas in the anemic hypertensives it is significantly lowered.