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This Article Full Text Full Text (PDF) All Versions of this Article: 295/3/E672    most recent 90441.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Miao, D. C. Articles by Rosenfeld, C. R. Search for Related Content PubMed PubMed Citation Articles by Miao, D. C. Articles by Rosenfeld, C. R.

Metabolism and synthesis of arginine vasopressin in conscious newborn sheep

Division of Neonatal-Perinatal Medicine, Department of Pediatrics, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas

Submitted 14 May 2008 ; accepted in final form 2 July 2008

Arginine vasopressin (AVP) is an important regulator of cardiovascular homeostasis in the fetus, but its role after birth is unclear. Although infused AVP increases mean arterial pressure (MAP) during the 1st mo after birth, pressor responses are unchanged, suggesting that vascular responsiveness is also unchanged. Alternatively, this could reflect increases in AVP metabolic clearance rate (MCR_AVP). However, newborn AVP metabolism and synthesis are poorly studied. Therefore, we examined the pressor responses to infused AVP and the pattern of circulating AVP, AVP production rate (PR_AVP), and MCR_AVP in conscious newborn sheep (n = 5) at 9–38 days after birth. Basal MAP rose and heart rate (HR) fell during the study period (P 0.02), while circulating AVP was unchanged (P > 0.1), averaging 3.01 ± 0.86 pg/ml. Infused AVP elicited steady-state responses at 10–40 min, increasing plasma AVP and MAP and decreasing HR (P < 0.001). Although pressor responses were unchanged between 9 and 38 days, the rise in MAP correlated with increases in plasma AVP (R = 0.47, P = 0.02, n = 24). MCR_AVP was unchanged throughout the 1st mo (P > 0.2), averaging 205 ± 17 ml·kg^–1·min^–1, and was associated with an elevated PR_AVP, 973 ± 267 pg·kg^–1·min^–1, which also was unchanged (P > 0.1). After birth, MCR_AVP and PR_AVP are elevated, probably accounting for the stable plasma AVP levels. The former is also likely to account for the stable pressor responses to infused AVP during the 1st mo. The reason for the elevated PR_AVP is unclear but may relate to increases in vascular volume associated with postnatal growth.

metabolic clearance rate; neonatal blood pressure; arginine vasopressin production rate