Prolactin-stimulated mitogenesis in the Nb2 rat lymphoma cell: lack of protoporphyrin IX effects.
Pharmacological characterization of the Nb2 cell peripheral-type benzodiazepine receptor (PBR) was determined using selected 1,4-benzodiazepines, PK 11195, and protoporphyrin IX (PPIX) to compete for specific [3H] Ro5-4864 binding. These data suggest that PPIX possesses an affinity for the Nb2 cell PBR (Ki = 142 nM). We have previously reported that the peripheral benzodiazepine ligands, Ro5-4864 and PK 11195, modulate prolactin-stimulated mitogenesis in the Nb2 cell(1). In contrast, PPIX, a putative endogenous ligand for the PBR had no effect on prolactin-stimulated mitogenesis in the Nb2 cell over the concentration range from 10(-15) M to 10(-6) M. Taken together these data show that PPIX has an affinity for the Nb2 cell PBR but does not modulate prolactin-stimulated mitogenesis at concentrations which should bind to the Nb2 cell PBR.
Gerrish
K E
KE
Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson 85721.
Putnam
C W
CW
Laird
H E
HE
D000818:Animals; D001570:Benzodiazepinones / Q000378:metabolism; D001667:Binding, Competitive; D007700:Kinetics; D008223:Lymphoma; D008938:Mitosis / Q000187:drug effects*; D011388:Prolactin / Q000494:pharmacology*; D011524:Protoporphyrins / Q000494:pharmacology*; D051381:Rats; D011963:Receptors, GABA-A / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D001570:Benzodiazepinones; D011524:Protoporphyrins; D011963:Receptors, GABA-A; C028513:4'-chlorodiazepam; D011388:Prolactin; C028025:protoporphyrin IX