In the sheep fetus, pulmonary and renal concentrations of angiotensin-converting enzyme (ACE) increase towards term in parallel with the prepartum surges in plasma cortisol and tri-iodothyronine (T(3)). The ontogenic change in pulmonary ACE has been shown to be induced, at least in part, by cortisol but the role of the thyroid hormones is unknown. Therefore, this study investigated the effects of thyroid hormones on tissue ACE concentration in fetal sheep during late gestation. Pulmonary and renal ACE concentrations were measured in sheep fetuses after experimental manipulation of thyroid hormone status by fetal thyroidectomy and exogenous hormone infusion. In intact fetuses, pulmonary and renal ACE concentrations increased between 127-132 and 142-145 days of gestation (term 145 +/- 2 days), coincident with the prepartum rises in plasma cortisol and T(3). The ontogenic increment in pulmonary ACE concentration was abolished when the prepartum surge in T(3), but not cortisol, was prevented by fetal thyroidectomy. At 143-145 days, ACE concentration in the lungs and kidneys of the thyroidectomised fetuses were both lower than those in the intact fetuses. In intact fetuses at 127-132 days, pulmonary ACE was upregulated by intravenous infusions of either cortisol (2-3 mg/kg per day) or T(3) (8-12 microg/kg per day) for 5 days. Renal ACE was unaffected by cortisol or T(3) infusion. Therefore, thyroid hormones have an important role in the developmental control of pulmonary and renal ACE concentration in the sheep fetus towards term. In addition, the prepartum rise in plasma T(3) appears to mediate, in part, the maturational effect of cortisol on pulmonary ACE concentration.

This article has been cited by other articles:

				D. M. O'Connor, D. Blache, N. Hoggard, E. Brookes, F. B. P. Wooding, A. L. Fowden, and A. J. Forhead Developmental Control of Plasma Leptin and Adipose Leptin Messenger Ribonucleic Acid in the Ovine Fetus during Late Gestation: Role of Glucocorticoids and Thyroid Hormones Endocrinology, August 1, 2007; 148(8): 3750 - 3757. [Abstract] [Full Text] [PDF]

				G. D. Giraud, S. Louey, S. Jonker, J. Schultz, and K. L. Thornburg Cortisol Stimulates Cell Cycle Activity in the Cardiomyocyte of the Sheep Fetus Endocrinology, August 1, 2006; 147(8): 3643 - 3649. [Abstract] [Full Text] [PDF]

				K. Chen, L. C. Carey, N. K. Valego, J. Liu, and J. C. Rose Thyroid hormone modulates renin and ANG II receptor expression in fetal sheep Am J Physiol Regulatory Integrative Comp Physiol, October 1, 2005; 289(4): R1006 - R1014. [Abstract] [Full Text] [PDF]