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.