FETAL ENDOCRINE RESPONSES TO PROLONGED REDUCED UTERINE BLOOD-FLOW AREALTERED FOLLOWING BILATERAL SECTIONING OF THE CAROTID-SINUS AND VAGUSNERVES

The present study examines the effect of carotid sinus/ vagosympatheti c denervation on fetal endocrine responses to prolonged reduced uterin e blood flow (RUBF). Fetal sheep had vascular catheters inserted follo wing bilateral sectioning of the carotid sinus and vagus nerves (dener vated, n=7) or sham denervation (intact, n=7). Uterine blood flow was mechanically restricted at 126.1 +/- 0.7 days (mean +/- S.E.M.) for 24 h, decreasing arterial oxygen saturation by 47.3+/-2.6% (P<0.01). Fet al plasma samples were obtained at -1, 3, 6, 12 and 24 h for subsequen t analyses of arginine vasopressin (AVP), angiotensin II and catechola mines. The AVP response to prolonged RUBF was markedly attenuated in d enervated fetuses (15.6+/-3.6 to 34.9+/-6.0 pg/ml) when compared with intact (10.0+/-1.4 to 127.3+/-28.4 pg/ml). In contrast, intact fetuses demonstrated no change in plasma angiotensin II concentrations with R UBF whereas denervated fetuses demonstrated a marked increase from 47. 5+/-18.9 to 128.7+/-34.2 pg/ml. The norepinephrine and epinephrine res ponses to prolonged RUBF were attenuated in denervated fetuses (950.1/-308.9 and 155.8+/-58.5 to 1268.3+/-474.6 and 290.6+/-160.2 pg/ml res pectively) when compared with intact (1558.3+/-384.4 and 547.3+/-301.7 pg/ml to 3289.2+/-1219.8 and 896.8+/- 467.8 pg/ml respectively). Thes e results support a role for the peripheral chemoreceptors in mediatin g fetal endocrine responses to prolonged RUBF, which may in part lead to the altered cardiovascular responses observed in denervated fetuses under these conditions.