Acute effects of angiotensin II in intact and adrenalectomized conscious dogs

Renal effects of A II, retention of sodium and water, may be mediated by the stimulation of aldosterone secretion and/or by direct effects of A II on the kidneys. An attempt was made to differentiate between these two possibilities. Methods: Conscious, female beagle dogs were used. The dogs were kept under standardized conditions (metabolic cage, daily sodium intake 4.5 mmol X kg-1 bw, chronically implanted arterial and venous catheters, i.v. hormone substitution after adrenalectomy by a portable pump). A II was infused i.v. over a period of 60 min after 60 min control. (Rate: 1, 4, 20 or 200 ng X min-1 X kg-1 bw). Results: Mean arterial blood pressure (MABP) increased with 20 and 200 ng A II X min-1 X kg-1 bw by an average of 34 mm Hg and 65 mm Hg resp. before and after adrenalectomy. Before adrenalectomy: sodium and water excretion decreased always at 4 and 20 ng A II X min-1 X kg-1 bw, whereas a rate of 200 ng A II X min-1 X kg-1 bw had different effects on renal sodium and water excretion. After adrenalectomy: sodium and water excretion decreased at 4 ng A II X min-1 X kg-1 bw. Whereas a rate of 20 and 200 ng. -As no marked alterations of the glomerular filtration rate occurred, sodium retention observed was mainly due to tubular effects of A II. Plasma aldosterone concentration increased at 4, 20 and 200 ng A II X min-1 X kg-1 bw in the intact dogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of intravenous epinephrine infusion on plasma renin activity in adrenalectomized dogs

Previous experiments have shown that circulating epinephrine stimulates renin secretin and increases plasma renin activity (PRA) when it is infused intravenously, but not when it is infused directly into the renal artery at similar infusion rates. The present experiments were designed to test the hypothesis that the adrenal glands mediate the PRA response to intravenous epinephrine infusion. Accordingly, anesthetized dogs were prepared with either an acute bilateral adrenalectomy or a sham-adrenalectomy procedure. Epinephrine was then infused intravenously into each animal for 45 minutes at a rate of 25 ng X kg-1 X min-1. Time control experiments in which epinephrine was not infused were also conducted. In sham-adrenalectomized dogs, PRA (in nanograms per ml h-1) rose from 4.1 +/- 1.4 in the control period to 13.0 +/- 3.0 during intravenous epinephrine infusion (means +/- SE; p less than 0.01). In adrenalectomized dogs, PRA rose from 2.1 +/- 0.4 during the control period to 5.5 +/- 0.9 during intravenous epinephrine infusion (p less than 0.01). Neither the absolute increments in PRA nor the percent increases in PRA were significantly different between the two groups receiving epinephrine. PRA remained unchanged in time control experiments. These data demonstrate that the adrenal glands need not be present in order for intravenous epinephrine infusion to elicit an increase in PRA. The data do not support the hypothesis, therefore, that epinephrine-induced increases in PRA are initiated by receptors located within the adrenal glands.     

Insulin and beta receptor modulation of K homeostasis in nephrectomized dogs with hyperkalemia

In nephrectomized dogs infused with 2 mEq KCl/kg/hr a homeostatic mechanism retards the development of hyperkalemia by transferring about 70% of the K load to intracellular fluid. beta Adrenergic receptor activity is importantly involved in the transfer process; halting it with propranolol reduces the proportion transferred to less than 35%. The addition of pancreatectomy increases the involvement of beta receptor activity; propranolol treatment now reduces the proportion transferred to less than 20%. Insulin treatment, on the other hand, not only improves transfer of a K load, it also alters the response to propranolol. Nephrectomized dogs treated with 2 U insulin/kg/hr deposit some 80% of the infused K in intracellular fluid. After beta receptor blockade, nearly 90% is transferred. The results suggest that in the K homeostatic mechanism of nephrectomized dogs, insulin and beta receptors may be reciprocally related. K transfer mediated by beta receptors improves after pancreatectomy, and insulin mediated K transfer improves after beta receptors are inactivated.     

Breed differences in dogs sensitivity to human points: A meta-analysis

The last decade has seen a substantial increase in research on the behavioral and cognitive abilities of pet dogs, Canis familiaris. The most commonly used experimental paradigm is the object-choice task in which a dog is given a choice of two containers and guided to the reinforced object by human pointing gestures. We review here studies of this type and attempt a meta-analysis of the available data. In the meta-analysis breeds of dogs were grouped into the eight categories of the American Kennel Club, and into four clusters identified by Parker and Ostrander [Parker, H.G., Ostrander, E.A., 2005. Canine genomics and genetics: running with the pack. PLoS Genet. 1, 507-513] on the basis of a genetic analysis. No differences in performance between breeds categorized in either fashion were identified. Rather, all dog breeds appear to be similarly and highly successful in following human points to locate desired food. We suggest this result could be due to the paucity of data available in published studies, and the restricted range of breeds tested.     

Olfactory sensitivity to {alpha}-ionone in humans and dogs

The ability of human subjects to detect -ionone was measuredover a range of concentrations and compared with that of GermanShepherd dogs measured previously under comparable conditions.The mean minimal concentration detected by humans was 4.0x10⁹molecules / cm³ which compares with a mean minimal concentrationof 4.0x10⁵ molecules / cm³ for the dogs. In general, dogs coulddetect -ionone in concentrations 1,000 to 10,000 times lowerthan could human subjects. Concentration-response curves forboth species are similar in form and show a double reversalin their upper ranges.     

Hypertension by nerve section in adrenalectomized, hypophysectomized, thyroidectomized and splanchnectomized dogs or in dogs with diabetes insipidus]

In the dog under anesthesia by pentobarbital, the acute hypertension by depressor buffer nerves section does not develop after adrenalectomy, hypophysectomy or thyro?dectomy. But this type of acute pressor response does appear normal in the dog parathyro?dectomized, splanchnicectomized or with hypothalamic diabetes insipidus.