In vitro binding and utilization of lipoproteins by luteal cells from ferrets treated with dopaminergic drugs during pseudopregnancy.
The effects of administration of dopaminergic drugs in vivo on the binding and utilization of lipoproteins for progesterone synthesis in vitro by ferret luteal cells were investigated. Pimozide, a dopamine antagonist, and bromoergocriptine (CB-154), a dopamine agonist, were administered to pseudopregnant ferrets to alter prolactin (PRL) concentrations daily beginning the day after ovulation. The control group received the vehicle solution only. Corpora lutea taken on Day 13 after ovulation were dissociated and the cells were incubated with canine lipoproteins, cyclic adenosine monophosphate (cAMP), and 5-cholesten-3 beta-25-diol (25-OH-cholesterol). Canine high-density lipoprotein (HDL) and low-density lipoprotein (LDL) stimulated progesterone accumulation by luteal cells from pimozide-treated animals but not from CB-154-treated ferrets. However, when 25-OH-cholesterol, which bypasses the LDL receptor, was provided as the substrate, steroidogenesis was stimulated in all groups. Together these observations suggest that dopaminergic alteration of PRL levels preferentially affects the utilization of lipoproteins. The uptake of canine HDL and LDL by luteal cells was saturable, and a high degree of cross-reactivity was observed. Heparin released surface-bound HDL and LDL, suggesting that HDL was binding to the LDL receptor. The quantity of LDL which could be released from luteal cells by heparin treatment was greater in animals treated with pimozide and decreased by treatment with CB-154, relative to luteal cells from control animals. It was concluded that the chronic administration of pimozide or CB-154 alters serum PRL levels in vivo, and influences the subsequent binding and utilization of lipoproteins by luteal cells in vitro. PRL may increase the number of LDL binding sites in luteal cells, thereby enhancing lipoprotein uptake for progesterone synthesis.
Rajkumar
K
K
Department of Biology, University of Saskatchewan, Saskatoon, Canada.
Martinuk
S D
SD
Agu
G O
GO
Murphy
B D
BD
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology*; D002335:Carnivora / Q000378:metabolism*; D003338:Corpus Luteum / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D005289:Ferrets / Q000378:metabolism*; D006493:Heparin / Q000378:metabolism; D006888:Hydroxycholesterols / Q000378:metabolism; D007700:Kinetics; D008074:Lipoproteins / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000494:pharmacology; D008077:Lipoproteins, LDL / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology*; D011374:Progesterone / Q000378:metabolism*; D011388:Prolactin / Q000097:blood; D011555:Pseudopregnancy / Q000378:metabolism*
D006888:Hydroxycholesterols; D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D010868:Pimozide; D001971:Bromocriptine; D011374:Progesterone; C007997:25-hydroxycholesterol; D011388:Prolactin; D006493:Heparin