DIGITALIS-LIKE FACTOR AND OUABAIN-LIKE COMPOUND IN PLASMA OF VOLUME-EXPANDED DOGS

Previous studies demonstrated that ouabain-like compound (OLC) is wide ly distributed in mammalian species and is found in a variety of diffe rent tissues. Although much evidence suggests that OLC is endogenous t o mammals, little information is available concerning physiological an d/or pathophysiological roles for OLC. In this study, genetic endogeno us digitalis-like factor (E-DLF) was measured using an enzyme bioassay and the more specific OLC was determined using ouabain antisera in pl asma drawn from dogs before and 30 and 120 min after massive volume ex pansion with isotonic saline. Plasma OLC was not changed by the saline load, whereas Na excretion was significantly elevated at the 30-min b lood draw and remained elevated at the 120-min blood draw. Because ren al exposure to OLC did not change with saline loading, it is unlikely that any portion of the profuse natriuresis in these animals could be attributed to OLC. In contrast, plasma E-DLF was higher after the sali ne load than before in each of four dogs at 30 and 120 min after the i nfusion. What portion of the profuse natriuresis can be attributed to E-DLF is unknown, although it is reasonable to assume that nanomolar l evels of pump inhibitor contributed to the natriuresis to some degree.