BACKGROUND: Adrenal blood flow (ABF) increases during hypoxemia in fetal sheep.
This report describes the application of FMS technology to the evaluation of
fetal adrenal function both in intact sheep fetuses and following removal of the
influence of the splanchnic nerve. Hypoxemia was used to challenge the adrenal.
METHODS: Vascular catheters were placed in 14 fetal sheep [bilateral SPLX (n=6) and control (CONT; n=8)] at ~120 days of gestation (dGA). At ~125 dGA, FMS were injected into the fetus before and during 60 min of fetal hypoxemia. The adrenals (separated into medulla and cortex) and reference blood samples were digested in potassium hydroxide solution, filtered, and the recovered FMS dissolved in Cellosolve®. Data, analyzed by Student's t-test, are expressed as mean±SEM.
RESULTS: Baseline ABF (whole, medulla, and cortex, respectively) for CONT was 365±56, 1119±255, and 172±32 ml/min/100g. This is similar to published values using radioactive spheres. SPLX baseline ABF did not differ from CONT. Hypoxemia increased whole, medullary, and cortical ABF from baseline for CONT by 281±35, 258±31, and 496±81% (p<0.05). The increase for SPLX was attenuated compared to CONT (p<0.05) for whole and medullary ABF (139±27 and 43±27%), but not cortical ABF.
CONCLUSIONS: 1) The FMS method is accurate and reproducible. 2) SPLX attenuates the hypoxemia-induced increase in ABF in fetal sheep primarily through a diminished medullary ABF response.
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