Nitric oxide regulation of corticotropin-releasing hormone release from the human perfused placenta in vitro.
We have investigated the regulatory role of nitric oxide (NO) in corticotropin-releasing hormone (CRH) release from the human perfused placental lobule in vitro. The effects of the NO donor sodium nitroprusside, the NO synthase inhibitor N omega-nitro-L-arginine, and the NO substrate L-arginine on human (h) placental CRH secretion have been studied. Single lobules of term placentae were bilaterally perfused with Krebs solution (5 mL/min; 95% O2-5% CO2; 37 C; pH 7.3). Fetal and maternal perfusates were collected at 4 C every 30 min for 3 h. CRH immunoreactivity (CRH-IR) in perfusates was measured by RIA using the 41-residue synthetic CRH as standard, 125I-labeled Tyr-hCRH as tracer, and a rabbit anti-CRH antibody Y2BO. The sensitivity of the assay was 0.13 pmol/L. Under basal conditions, human perfused placentae in vitro continuously secreted CRH-IR, which diluted in parallel to a synthetic hCRH-(1-41) standard curve. Size-exclusion chromatography of placental perfusates using a Sephadex G-50 column indicated that placental CRH-IR predominately coeluted with hCRH-(1-41) standard. Basal maternal perfusate CRH-IR levels (27 +/- 4 pmol/L) released from perfused placental lobules were nearly 10-fold greater than fetal perfusate CRH-IR levels (3.4 +/- 0.7 pmol/L; P < 0.05). Infusion of sodium nitroprusside (30-100 mumol/L) into the maternal and fetal placental circulations inhibited CRH-IR release into maternal perfusate in a concentration-dependent manner, but did not inhibit CRH-IR release into the fetal perfusate. N omega-nitro-L-arginine (100 mumol/L) increased placental CRH-IR secretion into fetal perfusate, and this effect was reversed by the infusion of L-arginine (100 mumol/L), which also reduced release below basal levels. In contrast, maternal perfusate CRH-IR levels were not affected by N omega-nitro-L-arginine or L-arginine. These results indicate that the human perfused placenta in vitro releases a substance of similar mol wt and hCRH-IR. Moreover, modulators of the NO signaling pathway differentially affect placental secretion of CRH-IR into the maternal and fetal perfusates. These data are consistent with the involvement of NO in the regulation of placental CRH release during pregnancy.
Roe
C M
CM
Maternal Health Research Center, John Hunter Hospital, Newcastle, New South Wales, Australia.
Leitch
I M
IM
Boura
A L
AL
Smith
R
R
D000293:Adolescent; D000328:Adult; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D009569:Nitric Oxide / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D019335:Nitroarginine; D009599:Nitroprusside / Q000494:pharmacology; D010477:Perfusion; D010920:Placenta / Q000187:drug effects* / Q000378:metabolism*; D011247:Pregnancy
D004791:Enzyme Inhibitors; D009599:Nitroprusside; D019335:Nitroarginine; D009569:Nitric Oxide; D003346:Corticotropin-Releasing Hormone; D001120:Arginine; D019001:Nitric Oxide Synthase