FETAL SHEEP ADRENAL BLOOD-FLOW RESPONSES TO HYPOXEMIA AFTER SPLANCHNICOTOMY USING FLUORESCENT MICROSPHERES

Adrenal gland blood flow (ABF) increases during hypoxemia in fetal she ep, but regulation of ABF is poorly understood. The purpose of this st udy was to determine the effects of splanchnic nerve section on fetal ABF responses to hypoxemia using the fluorescent microsphere (FM) tech nique. At 125 days of gestation, 14 unanesthetized fetal sheep [bilate ral splanchnicotomy (Splx, n = 6) and control (Cent, n = 8)] were inje cted with FM before and at 60 min of N-2-induced hypoxemia (similar to 40% decrease in fetal arterial PO2). Adrenal tissue and reference blo od samples were digested and filtered, and FM dye was extracted for sp ectrometer analysis. Baseline whole, medullary, and cortical ABF for t he Cent group were similar to published values using radioactive micro spheres and did not differ from Splx values. Hyperemia increased whole , medullary, and cortical ABF (mean +/- SE) from baseline for the Cent group by 281 +/- 35, 258 +/- 31, and 496 +/- 81% (P < 0.05). The incr ease for the Splx group was attenuated compared with the Cent group (P < 0.05) for whole and medullary ABF (139 +/- 27 and 43 +/- 27%) but n ot cortical ABF (326 +/- 91%). We conclude that 1) the FM technique is valid for measuring fetal ABF and 2) in fetal sheep the splanchnic ne rve is not necessary to maintain basal ABF but plays an important role in regulating the hypoxemia-induced increase in ABF through the medul lary, but not cortical, ABF response.