title: The biological meaning of progesterone levels.
abstract: The effect of systematically delayed progesterone treatment was examined in 45 pregnant rats near term. Progesterone (P) and prostaglandin F (PGF) were measured in uterine vein plasma and uterine tissue before and during spontaneous labor or during prolonged pregnancy. Control animals exhibited the expected P-withdrawal (Pw) prior to spontaneous labor and properly timed P-treatment predictably prevented Pw and labor. However, when P was administered 11.7 +/- 2.8 hours (Mean +/- S.E.) before spontaneous labor, the animals delivered normally despite increased plasma and tissue P-levels. These observations show that P-concentration can not be equated to P-action. Thus, when high P-levels are measured near term, as in parturient women, the biological ACTION of this hormone on uterine function should be cautiously interpreted.
mesh_terms: D000818:Animals; D005260:Female; D007743:Labor, Obstetric / Q000187:drug effects*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood* / Q000494:pharmacology; D011460:Prostaglandins F / Q000097:blood*; D051381:Rats; D014599:Uterus / Q000098:blood supply / Q000502:physiology*
chemical_list: D011460:Prostaglandins F; D011374:Progesterone