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Effects of fetal ovine adrenalectomy on sympathetic and baroreflex responses at birth. Am J Physiol Regul Integr Comp Physiol 2002 Aug;283(2):R460-7

Date

07/18/2002

Pubmed ID

12121859

DOI

10.1152/ajpregu.00056.2002

Scopus ID

2-s2.0-0036340398   13 Citations

Abstract

Studies were performed to test the hypothesis that the absence of adrenal glucocorticoids late in gestation alters sympathetic and baroreflex responses before and immediately after birth. Fetal sheep at 130-131 days gestation (term 145 days) were subjected to bilateral adrenalectomy before the normal prepartum increase in plasma cortisol levels. One group of fetuses (n = 5) received physiological cortisol replacement with a continuous infusion of hydrocortisone (2 mg x day(-1) x kg(-1) for 10 days), whereas the other group received 0.9% NaCl vehicle (n = 5). All animals underwent a second surgery 48 h before the study for placement of a renal nerve recording electrode. Heart rate (HR), mean arterial blood pressure (MABP), renal sympathetic nerve activity (RSNA), and baroreflex control of HR and RSNA were studied before and after cesarean section delivery. At the time of study (140-141 days gestation), fetal plasma cortisol concentration was undetectable in adrenalectomized (ADX) fetuses and 58 +/- 9 ng/ml in animals receiving cortisol replacement (ADX + F). Fetal and newborn MABP was significantly greater in ADX + F relative to ADX animals. One hour after delivery, MABP increased 13 +/- 3 mmHg and RSNA increased 91 +/- 12% above fetal values in ADX + F (both P < 0.05) but remained unchanged in ADX lambs. The midpoint pressures of the fetal HR and RSNA baroreflex function curves were significantly greater in ADX + F (54 +/- 3 and 56 +/- 3 mmHg for HR and RSNA curves, respectively) than ADX fetuses (45 +/- 2 and 46 +/- 3 mmHg). After delivery, the baroreflex curves reset toward higher pressure in ADX + F but not ADX lambs. These results suggest that adrenal glucocorticoids contribute to cardiovascular regulation in the late-gestation fetus and newborn by modulating arterial baroreflex function and sympathetic activity.

Author List

Segar JL, Van Natta T, Smith OJ

Author

Jeffrey L. Segar MD Professor in the Pediatrics department at Medical College of Wisconsin




MESH terms used to index this publication - Major topics in bold

Adrenalectomy
Animals
Animals, Newborn
Baroreflex
Blood Pressure
Cesarean Section
Drug Administration Routes
Female
Fetus
Heart Rate
Heart Rate, Fetal
Hormone Replacement Therapy
Hydrocortisone
Kidney
Pregnancy
Sheep
Sympathetic Nervous System
jenkins-FCD Prod-486 e3098984f26de787f5ecab75090d0a28e7f4f7c0