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Hyperosmolality elevates plasma atrial natriuretic factor in the ovine fetus
C Y Cheung1, L K Miner, R A Brace
1Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093.
The American Journal of Physiology
|October 1, 1989
Summary
Hyperosmolality significantly increases fetal plasma atrial natriuretic factor (ANF) in sheep fetuses. This suggests hyperosmolality, not just volume expansion, triggers ANF release during fetal stress.
Area of Science:
- Perinatal Physiology
- Endocrinology
- Fetal Medicine
Background:
- Atrial natriuretic factor (ANF) plays a crucial role in fluid and electrolyte balance.
- Understanding fetal responses to osmotic stress is vital for perinatal care.
Purpose of the Study:
- To investigate the impact of hyperosmolality on fetal plasma ANF concentrations in ovine models.
- To differentiate the effects of hyperosmolality versus volume expansion on fetal ANF.
Main Methods:
- Chronically catheterized ovine fetuses (133 days gestation) received infusions of isotonic or hypertonic solutions (NaCl, mannitol).
- Fetal plasma osmolality and ANF levels were measured before and after infusions.
- Blood volume and venous pressure changes were monitored.
Main Results:
- Hypertonic infusions significantly increased fetal plasma osmolality and ANF levels compared to isotonic infusions.
- The magnitude of ANF increase correlated with the degree of hyperosmolality.
- ANF and venous pressure returned to baseline within 1 hour, despite sustained hyperosmolality.
Conclusions:
- Hyperosmolality, independent of acute volume expansion, is a potent stimulus for fetal ANF release.
- The transient nature of the ANF response suggests a direct but temporary effect of hyperosmolality or potentiation of volume expansion effects.