Prostaglandins induce proliferation of rat hepatocytes through a prostaglandin E2 receptor EP3 subtype.
We characterized the proliferative action of prostaglandins (PGs) in relation to their membrane receptors on rat hepatocytes in primary culture. PGs in the order 16,16-dimethyl PGE2 > PGE2 > PGF2alpha >> PGD2 augmented epidermal growth factor (EGF)/insulin-induced DNA synthesis, assessed by [(3)H]thymidine incorporation, in a concentration-dependent manner, whereas PGs alone did not stimulate basal DNA synthesis without EGF and insulin. The cells exhibited [(3)H]PGE2 binding sites that were displaced by unlabeled PGs in the order PGE1 = PGE2 > PGF2alpha > PGD2. PGE2 inhibited glucagon-stimulated adenosine 3',5'-cyclic monophosphate (cAMP) accumulation concentration dependently. The mean effective concentration for DNA synthesis, median inhibitory concentration for cAMP accumulation, and dissociation constant for [(3)H]PGE2 binding at 25 degrees C were almost identical (approximately 70 nM). Treatment of the cells with pertussis toxin (100 ng/ml), which ADP-ribosylated most of the 41-kDa substrate, abolished the proliferative effects of PGs. We detected the expression of mRNA of the EP3 subtype PGE2 receptor using reverse transcription-polymerase chain reaction. Moreover, an EP3 agonist, enprostil, but not the EP1 agonist 17-phenyl-trinor-PGE2 or the EP2/EP4 agonist 11-deoxy-PGE1, stimulated EGF/insulin-induced DNA synthesis. These results indicate that PGs act as comitogenic growth factors through the EP3 subtype PGE2 receptor coupled with G(i) protein in cultured rat hepatocytes.
Hashimoto
N
N
First Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Watanabe
T
T
Ikeda
Y
Y
Yamada
H
H
Taniguchi
S
S
Mitsui
H
H
Kurokawa
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D015232:Dinoprostone / Q000502:physiology*; D016620:Enprostil / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006133:Growth Substances / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D008099:Liver / Q000166:cytology*; D008297:Male; D037342:Pertussis Toxin; D051381:Rats; D017208:Rats, Wistar; D018078:Receptors, Prostaglandin E / Q000502:physiology*; D058308:Receptors, Prostaglandin E, EP3 Subtype; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D006133:Growth Substances; D007328:Insulin; C545649:Ptger3 protein, rat; D018078:Receptors, Prostaglandin E; D058308:Receptors, Prostaglandin E, EP3 Subtype; D010566:Virulence Factors, Bordetella; D004815:Epidermal Growth Factor; D037342:Pertussis Toxin; D016620:Enprostil; D015232:Dinoprostone; D002118:Calcium