Ontogeny of renal hemodynamic response to terbutaline and forskolin in sheep.
The renal hemodynamic response to renal arterial infusions of terbutaline and forskolin were compared in chronically instrumented fetal (129-139 days gestation; term 145 days), newborn (7-14 days old) and nonpregnant adult sheep. Infusions of terbutaline produced renal vasodilation in all age groups with maximal increases being higher in fetal (47 +/- 7%) than in newborn (30 +/- 8%) or adult sheep (24 +/- 5%). Terbutaline-mediated renal vasodilation was inhibited by the selective beta 2 adrenoceptor antagonist, ICI 118,551, whereas infusion of selective beta 1 adrenoceptor antagonist, ICI 89,406, had no effect. Moreover, terbutaline effects were unchanged after phentolamine infusion to inhibit potential antagonistic effects of neuronal norepinephrine release by presynaptic beta 2 adrenoceptor stimulation. Renal arterial infusion of forskolin produced renal vasodilation of similar magnitude in all age groups, with maximal increases of 46 +/- 5, 38 +/- 3 and 38 +/- 5% in fetal, newborn and adult sheep, respectively. Taken together, these results suggest that renal vasodilatory mechanisms stimulated by selective activation of beta 2 adrenoceptors (terbutaline) are greater during fetal life. However, direct activation of adenylate cyclase with forskolin produces essentially similar renal vasodilatory responses during development in sheep. Thus, reasons to explain age-dependent differences in renal vasodilation observed previously with endogenous catecholamines may be at the receptor-hormone level.
Nakamura
K T
KT
Department of Pediatrics, University of Iowa College of Medicine, Iowa City.
Alden
B M
BM
Matherne
G P
GP
Jose
P A
PA
Robillard
J E
JE
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D007668:Kidney / Q000098:blood supply* / Q000254:growth & development; D011247:Pregnancy; D011412:Propanolamines / Q000494:pharmacology; D012756:Sheep / Q000254:growth & development*; D013726:Terbutaline / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects
D011412:Propanolamines; D005576:Colforsin; C026777:ICI 118551; C025716:ICI 89406; D013726:Terbutaline