Water diuresis from clonidine (catapres).

The renal hemodynamic and excretory effects of clonidine were tested in two groups of dogs. In one group, the drug was given directly into the renal artery at a rate of 1.2 mug/min and resulted in a significant decrease of the effective renal plasma flow (ERPF) in both kidneys, an increase in filtration fraction (FF), urine volume (UV), and free water clearance (CH2O) and had no effect upon the glomerular filtration rate (GFR), osmolar clearance (Cosm) and the excretion of sodium (UNaV), chloride (UC1V), potassium (UKV), calcium (UCaV) and phosphorous (UPO4V). No unilateral effect was appreciated. In the second group of animals it was given intravenously at a rate of 12.0 mug/min and resulted in a significant decrease of ERPF, UNaV, UC1V, and increase in FF, UV, and CH2O) but had no effect upon GFR, Cosm, UKV, UCaV and UPO4V. Systemically it decreased heart rate (H.R.) and respiratory rate (R.R.) in both groups of animals; it increased blood pressure (BP) in Group 1 and had no effect on BP in Group 2.

Direct renal hemodynamic effects of clonidine.

The renal hemodynamic and excretory effects of clonidine were tested in 2 groups of dogs. In one group, the drug was given directly into the renal artery at a rate of 1.2 mug/min and resulted in a significant decrease of the effective renal plasma flow (ERPF) in both kidneys, an increase in filtration fraction (F.F.), urine volume (U.V.), and free water clearance (CH2O) and had no effect upon the glomerular filtration rate (GFR), osmolar clearance (Cosm) and the excretion of sodium (UNa+V), chloride (UC1-V), potassium (UK+V), calcium (UCa++V) and phosphorous (UP04V). In the second group of animals it was given intravenously at a rate of 12.0 mug/min and resulted in a significant decrease of ERPF, UNa+V, UC1-V, and an increase in F.F., U.V. and CH2O and had no effect upon GFR, Cosm, UK+V, UCa++V and UPO4V. Systemically, it decreased heart rate (H.R.) and respiratory rate (R.R.) in both groups of animals; it increased blood pressure (BP) in Group I and had no effect on BP in Group II.

Direct renal hemodynamic effects of two vasodilators: diazoxide and acetylcholine.

The direct renal hemodynamic effect of two different vasodilators, diazoxide and acetylcholine, in the anesthetized dog, were studied. In 12 dogs (Group 1), diazoxide was given first directly into the renal artery and was followed by the addition of acetylcholine. In 6 dogs (Group 2) the order of drug administration was reversed. The glomerular filtration rate (GFR), the effective renal plasma flow (ERDF), and the excretion of sodium, potassium, chloride, and urine output were determined for both control and experimental (infused) kidneys. Both drugs when given alone resulted in a significant increase of all parameters tested on the experimental kidney, except the ERPF which was spuriously decreased by diazoxide. The addition of either drug upon the first given did not produce and further effect. It was, therefore, concluded that the hemodynamic changes, as well as the handling of electrolytes and water by the kidney, were solely due to the vasodilating properties of both compounds. A local renal tubular effect by diazoxide concerning sodium excretion could not be substantiated by our studies.