The modulation of placental lactogen release by opioids: a role for extracellular calcium.
We previously reported that kappa opioids stimulated the release of human placental lactogen (hPL) from trophoblastic cells and that this effect was prevented by co-incubation with naloxone. We also reported that adenylate cyclase was not directly involved in this process. In order to understand the post-receptor events mediating hPL release by opioids in the human placenta, we studied the role of extracellular calcium. Human trophoblastic cells obtained by trypsin digestion were cultured for 48 h in Ham's F-10 medium supplemented with 10% fetal bovine serum (FBS), 200 U/ml penicillin, and 200 micrograms/ml streptomycin. 45Ca2+ influx was then measured by filtration on glass-fiber filters. We observed a time- and dose-dependent stimulation of 45Ca2+ influx by ethylketocyclazocine (EKC) with an EC50 of 0.5 nM and a maximal stimulation of 196% over control. This effect was completely blocked by naloxone, a non-specific opioid antagonist, and by nor-binaltorphimine, a specific kappa antagonist. We also demonstrated that U-50,488 (kappa agonist) had the same stimulatory effect as EKC (221 +/- 25% of control). D-Ala2,NMe-Phe4,Gly-ol5)-enkephalin (DAGO) (mu agonist) slightly stimulated Ca2+ influx (128 +/- 5% of control, p > 0.05) whereas D-Ser2,Leu,Thr6)-enkephalin (DSLET) (delta agonist) had no effect. Pre-incubation of trophoblastic cells with pertussis toxin (PTX) did not affect the EKC-induced 45Ca2+ influx, suggesting that this placental opiate effect is not coupled with PTX-sensitive G proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
Petit
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A
Department of Obstetrics and Gynecology, Faculty of Medicine, University of Montreal, Quebec, Canada.
Gallo-Payet
N
N
Bellabarba
D
D
Lehoux
J G
JG
Bélisle
S
S
D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D037361:Adenylate Cyclase Toxin; D000700:Analgesics / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D004745:Enkephalins / Q000494:pharmacology; D016314:Ethylketocyclazocine / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D037342:Pertussis Toxin; D010928:Placental Lactogen / Q000378:metabolism*; D011759:Pyrrolidines / Q000494:pharmacology; D013997:Time Factors; D014327:Trophoblasts / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D000700:Analgesics; D004745:Enkephalins; D009294:Narcotics; D011759:Pyrrolidines; D010566:Virulence Factors, Bordetella; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; C051843:binaltorphimine; D009270:Naloxone; D015759:Ionomycin; D016314:Ethylketocyclazocine; D004743:Enkephalin, Leucine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C034318:enkephalin, Ser(2), Leu(5), Thr(6)-; D010928:Placental Lactogen; D037342:Pertussis Toxin; D002118:Calcium; D004298:Dopamine