Abstract
β 2- adrenergic induced renal vasodilatation is greater in fetal than adult sheep. To determine a mechanism involved in this age related response, we characterized the β adrenoceptor in fetal and adult renal cortical membranes (30,000 xg fraction containing both vascular and tubular membranes) using radioligand binding studies. Specific binding of the non-selective β adrenergic antagonist 125I-pindolol (defined by 1 uM (-)-propranolol) was 80%. Receptor density from Rosenthal plots (Bmax, fmol/mg protein), inhibition constant (Ki, M), and % distribution of receptor subtypes using the β2 adrenergic antagonist, ICI 118, 551, from competition experiments (M±SE) are:
Ki for (-)-isoproterenol and the β2 agonist zinterol were similar in both fetus and adult. However, stereoselectivity was greater in adults than fetuses: similar Ki for (-)-propranolol but Ki for (+)-propranolol less in fetus (6E−8M) (n=3) than adult (1E-7M)(n=3), (p<.05 ANOVA).
We conclude that β adreceptors in fetal kidneys are less differentiated than those in adults. The greater density of β2 receptors in fetal kidneys may explain in part the greater β2 vasodilatory response in fetal than adult kidneys.
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McKelvey, T., Felder, C., Nakamura, K. et al. MULTIPLE β -ADRENOCEPTORS ARE PRESENT IN ADULT BUT NOT FETAL SHEEP KIDNEYS. Pediatr Res 21 (Suppl 4), 218 (1987). https://doi.org/10.1203/00006450-198704010-00310
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DOI: https://doi.org/10.1203/00006450-198704010-00310
