title: Renal circulatory effects of adrenergic stimuli in anesthetized piglets and mature swine.
abstract: The relative maturity of renal circulatory responses to efferent renal nerve stimulation, and to exogenous norepinephrine and isoproterenol, was tested in 62 piglets (1--16 days old) under pentobarbital anesthesia (10--25 mg/kg). Aortic pressure, heart rate, and renal and femoral arterial flows (measured by electromagnetic flow transducers) were recorded simultaneously. Renal vascular resistance was calculated as mean aortic pressure/mean flow. Transection of the renal nerve resulted in decreased renal resistance in all animals. Efferent renal nerve stimulation at increasing frequencies (2--12.5 Hz, at 1.2 ms pulse duration and 1.0 mA current) showed age-dependent differences in the threshold and also in the magnitude of increase in renal resistance. Norepinephrine (0.05--1.0 microgram/kg) caused age-dependent increases in renal resistance. Restoration of renal flow toward control level occurred during the peak pressor effect of norepinephrine only in older piglets. Isoproterenol (0.05--1.0 microgram/kg) did not alter renal resistance consistently in piglets younger than 1 wk. Phentolamine (0.25 mg/kg) attenuated or blocked resistance increases to 0.5 microgram norepinephrine/kg or to renal nerve stimulation at 12.5 Hz in all animals. Propranolol (0.1 mg/kg) attenuated or blocked resistance decreases to 0.1 microgram isoproterenol/kg, which occurred only in older piglets. These results indicate the presence of an active alpha-adrenergic vasoconstrictor mechanism and absence of the beta-adrenergic vasodilator mechanism in the renal circulation of swine at birth.
mesh_terms: D000375:Aging; D000818:Animals; D004558:Electric Stimulation; D007545:Isoproterenol / Q000494:pharmacology*; D007668:Kidney / Q000098:blood supply* / Q000294:innervation; D009638:Norepinephrine / Q000494:pharmacology*; D012039:Regional Blood Flow / Q000187:drug effects; D013552:Swine; D013564:Sympathetic Nervous System / Q000502:physiology*; D014655:Vascular Resistance / Q000187:drug effects
chemical_list: D007545:Isoproterenol; D009638:Norepinephrine