The Comparative Hemodynamic Effects of Propranolol in Chronically Instrumented Puppies and Adult Dogs

Abstract

To determine if there are age-related changes in response to propranolol, we studied the hemodynamic effects of this β-adrenergic-blocking agent in 19 awake chronically instrumented puppies and compared the response to that of 9 awake chronically instrumented adult dogs. Following intravenous administration of 1 mg/kg propranolol, heart rate, cardiac output, stroke volume, systemic arterial mean blood pressure and systemic vascular resistance were reduced similarly in all age groups of animals. However, puppies were more sensitive to the β-adrenergic-blocking effect of propranolol than adult dogs when stressed with isoproterenol.

Cardiovascular and Renal Effects of Isoproterenol Infusions in Young Swine

“…Our findings in adult swine given single injections of this compound [1,25] demonstrate that mature swine are comparable to other adult mam mals with respect to their cardiovascular re sponses to ISP. Furthermore, we have ob served a 150% increase in RV dP/dtmax, a 30% increase in RBF and a 13% decrease in In young swine, we found that systemic infusions of ISP elicited positive inotropic and chronotropic responses (table II) com patible with the recent findings of high den sity of P-adrenergic binding sites in the hearts of 1-week-old dogs [26], The aortic pressure and HR effects (table II) were also within the range observed during infusions of 0.1 and 0.2 pg/kg/min in young dogs either conscious [7] or anesthetized with pentobarbital [6]. The decreased RVR in young swine (table II) contrasts with the increased RVR observed in similarly anesthetized dogs aged 3-65 days given ISP infusions at 0.05-1.0 pg/kg/min [6], During i.a.…”

“…The cardiovascular effects of ISP adminis tered systemically in adult mammals include increased HR and cardiac contractile func tion [11,12], and increased renal and femoral blood flows [13,19,20], although a recent dose-response study in conscious dogs showed no change in RBF [7]. Our findings in adult swine given single injections of this compound [1,25] demonstrate that mature swine are comparable to other adult mam mals with respect to their cardiovascular re sponses to ISP.…”

“…ISP infusion in young swine, we also observed a sustained decrease in resistance in the perfused left kidney (ta ble IV) which confirmed our previous dem onstration that renal p-adrenergic vasodila tion occurs in piglets older than 1 week as well as in mature swine [1,25]. The lack of a greater decrease in RVR during direct renal infusion of the same ISP doses (table IV) that produced a 19% decrease in RVR when given systemically (table II) may be a conse quence of immaturity of the renal p-adrenergic vasodilator response and the relatively flat dose-response relationship within the range of a 2-or 5-fold increase in ISP dose [1,7,[18][19][20], The contrasting results of the puppy and piglet studies contribute to our impression of a species difference in the rate of maturation of cardiovascular function in dogs and swine.…”

“…or i.a. were compared by ANOVA and found to be indistinguishable, as suggested by earlier observations of the effects of narrow dose ranges in young swine [1] or dogs [7] and in adult dogs [7,[18][19][20]. Data were therefore combined and results are reported for the range 0.1-0.2 pg/kg/min in order to simplify the pre sentation of data on the effects of i.v.…”

“…The effects of continuous infusions of cardiotonic doses of norepinephrine and dopamine on glomerular filtration rate (GFR) in the developing kid ney have also been examined [4], This report deals with the effects of another clinically useful catecholamine, isoproterenol (ISP), on the developing kidney. Although effects of ISP on cardiac dynamics [5][6][7], renal hemo dynamics [6,7] and the renin-angiotensin system [8] have been investigated in young mammals, renal function studies were not carried out. We therefore undertook to exam ine GFR and water and sodium excretion in swine old enough to demonstrate renal vas cular responses to ISP [1] but young enough to exhibit immaturity of renal function [9,10].…”