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Progesterone receptors and ventilatory stimulation by progestin
Journal of Applied Physiology (Bethesda, Md. : 1985)
|February 1, 1986
Summary
Progestin stimulates breathing, but its effectiveness varies. This study found that both increased progestin levels and progesterone receptor numbers are necessary for progestin to effectively enhance ventilation.
Area of Science:
- Reproductive Endocrinology
- Respiratory Physiology
Background:
- Progestins are known to influence respiratory control, but their efficacy as ventilatory stimulants is inconsistent.
- The role of progesterone receptors in mediating the ventilatory response to progestins requires further elucidation.
Purpose of the Study:
- To investigate the hypothesis that progesterone receptor levels determine the ventilatory response to progestin.
- To compare the ventilatory effects of medroxyprogesterone acetate (MPA) with or without estradiol in ovariectomized rats.
Main Methods:
- Ovariectomized rats were treated with MPA alone, estradiol alone, MPA plus estradiol, or vehicle (saline).
- Ventilation, arterial PCO2, and PO2 were measured.
- Progesterone receptor levels in uterine tissue were quantified.
Main Results:
- MPA alone, with low progesterone receptor levels, did not alter ventilation.
- Combined MPA and estradiol treatment, which increased progesterone receptor levels, significantly raised ventilation and lowered arterial PCO2.
- Estradiol alone increased progesterone receptors but did not affect ventilation or PCO2, while decreasing PO2.
Conclusions:
- Both elevated progestin levels and sufficient progesterone receptor numbers are essential for progestin to act as a ventilatory stimulant.
- The combination of estradiol and MPA demonstrates a synergistic effect on ventilation and CO2 regulation.