Dose-dependent cardiovascular, renal, and endocrine effects of furosemide in conscious lambs.

In recent experiments in conscious lambs, we showed that in addition to its well-known natriuretic and diuretic effects, i.v. injection of 2 mg/kg of furosemide resulted in a sustained increase in heart rate and an age-dependent increase in plasma renin activity. To determine whether these responses were dose dependent, we measured various parameters of cardiovascular, renal, and endocrine function in six chronically instrumented lambs. Three of seven doses of furosemide were tested at 48-h intervals; the range of doses was 0 to 7.5 mg/kg. A dose-dependent transient pressor response occurred within 20 min of furosemide administration; the duration of this response increased with increasing doses. Heart rate increased 40 min after doses of furosemide > or = 0.25 mg/kg; this response was not dose dependent. Renin increased following all doses; the peak and the duration of the renin response were dose dependent. These data provide new information on the dose-dependent cardiovascular, renal, and endocrine responses to furosemide in conscious newborn lambs.