Effect of dexamethasone on pulmonary and renal angiotensin-converting enzyme concentration in fetal sheep during late gestation

Abstract

Objectives The effect of dexamethasone on tissue angiotensin-converting enzyme (ACE) was investigated in fetal sheep. Study design Pulmonary and renal ACE concentrations were measured in 16 sheep fetuses at between 127 and 131 days of gestation (term 145±2 days): 6 were untreated, whereas 10 were chronically catheterized and infused intravenously with either saline solution (0.9%, n = 4) or dexamethasone (45-60 μg · kg −1 · d −1, n = 6) for the previous 2 days. The dexamethasone dose increased plasma dexamethasone to around one fifth of that measured in newborn human infants delivered after maternal dexamethasone treatment. Results Over the period of infusion, arterial blood pressure increased significantly in the dexamethasone (+6.8±1.5 mm Hg, P<.05) but not saline-treated fetuses (+1.6±0.6 mm Hg). At delivery, pulmonary ACE in the dexamethasone-infused fetuses (1.24±0.26 nmoles hippurate · min −1 · mg protein −1) was significantly greater than in the control fetuses (0.50±0.07 nmoles · min −1 · mg protein −1, P<.005); renal ACE was unchanged by dexamethasone treatment. Overall, pulmonary ACE and blood pressure were correlated on the last day of infusion ( r = 0.70, P<.05). Conclusion The rise in pulmonary ACE seen in dexamethasone-treated sheep fetuses may contribute, in part, to the glucocorticoid-induced increase in blood pressure.