| Autor: |
Docherty CC; Laboratory for Pregnancy and Newborn Research, Department of Biomedical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA., Kalmar-Nagy J, Engelen M, Koenen SV, Nijland M, Kuc RE, Davenport AP, Nathanielsz PW |
| Jazyk: |
angličtina |
| Zdroj: |
American journal of physiology. Regulatory, integrative and comparative physiology [Am J Physiol Regul Integr Comp Physiol] 2001 Jul; Vol. 281 (1), pp. R261-8. |
| DOI: |
10.1152/ajpregu.2001.281.1.R261 |
| Abstrakt: |
At 110-111 days gestation, instrumented fetal sheep were administered saline or dexamethasone (2.2 microgram. kg(-1). h(-1) iv) for 48 h. Measurement of fetal blood pressure showed a greater increase in dexamethasone-treated (n = 6) compared with control (n = 5) fetuses (7.3 +/- 2.3 vs. 0.6 +/- 2.3 mmHg, P < 0.05). Fetuses were delivered by cesarean section, and the femoral muscle and brain were obtained under halothane anesthesia. Femoral and middle cerebral arteries (approximately 320-micrometer internal diameter) were evaluated using wire myography. Sensitivity to KCl (2.5-125 mM) and the magnitude of the maximal vasoconstriction to 125 mM K(+) were similar in femoral and middle cerebral arteries from dexamethasone-treated vs. control fetuses. Acetylcholine-induced vasorelaxation was similar in femoral arteries from control and dexamethasone-treated fetuses. Middle cerebral arteries did not relax to acetylcholine. Sensitivity to endothelin-1 (ET-1; 0.1 pM-0.1 microM) and magnitude of the ET-1-induced vasoconstriction were greater in femoral arteries from dexamethasone-treated vs. control fetuses (P < 0.05). Autoradiographical studies with receptor-specific ligands demonstrated increased ET(A)-receptor binding, the principal receptor subtype, in femoral muscle vessels (P < 0.001) but decreased ET(A)-receptor binding in middle cerebral arteries (P < 0.01) from dexamethasone-treated compared with control fetuses. Relatively little ET(B)-receptor binding was evident in all tissues examined. We conclude that hyperreactivity to ET-1, due to increased ET(A)-receptor binding, may be involved in the dexamethasone-induced increase in peripheral vascular resistance in fetal sheep in vivo. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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