Multiple Β -Adrenoceptors Are Present in Adult but Not Fetal Sheep Kidneys

Abstract

e d i a t r i c s , Providence, Rhode I s l a n d , and Genetics I n s t i t u t e , Cambridge, Massachusetts EP regulates erythropoiesis i n t h e f e t u s (F) , newborn (N), and juvenile (J). Delineating the developmental changes t h a t occur i n EP k i n e t i c s would be important i n explaining the possible r o l e t h a t EP plays i n the pathophysiology of anemia and polycythemia. W e investigated t h e differences i n EP k i n e t i c s i n the F, N, and J by infusing 3 5~ l a b e l l e d human Ep i n t o 5 F (126 day), 6 N (7-8 day), and 4 J (270 day) sheep. After bolus infusion, timed blood samples were obtained and the plasma was p r e c i p i t a t e d with 20% t r i c h l o r o a c e t i c a c i d. Plasma h a l f l i f e (Tb), volume of d i s t r i b u t i o n (Vd) and EP clearance (Cep) were determined from t h e b e t a decay curves of I n EP vs time : Group Tk (hours) .Vd (ml-kg-l) cep (ml.kg-lsmin-J-) Fetus (F) *16.3 f 4.7 516 f 182 0.36 f 0.05 Newborn (N) 11.2 f 3.6

Ontogeny of Renal β-Adrenoceptor-Mediated Vasodilation in Sheep: Comparison between Endogenous Catecholamines

“…p2-Adrenergic receptor density may be greater in fetal renal vessels compared to vessels from newborn and adult sheep. In support of this hypothesis is the preliminary report suggesting that renal cortical membranes (containing both vascular and tubular membranes) from fetal kidneys contains a greater density of P2-adrenoceptors than kidneys from adults (27). Moreover, stereoselectivity of the &adrenoceptor was greater in adult than fetal renal cortical membranes suggesting that P-adrenoceptors may be less differentiated into specific ,L?-adrenoceptor subtypes in immature animals (27).…”