Effects of phospholipases on ornithine decarboxylase activity in mammary gland explants from midpregnant mice.
Phospholipases A2 (PLA2) and C (PLC) stimulate ornithine decarboxylase (ODC) activity in mouse mammary gland explants preincubated with insulin and cortisol. PLC concentrations of 0.1 micrograms/ml produced responses that were close in magnitude to that of PRL, whereas PLA2 at concentrations of 5-50 micrograms/ml was 35-40% as efficacious as 1 microgram/ml PRL in stimulating ODC activity. The time courses of PLC, PLA2, and PRL actions on ODC activity were not different from one another. When PRL and PLC were tested together, a response greater than the sum of the responses of each of these agents alone was observed; PLA2 (25 micrograms/ml) when tested with PRL produced a nonadditive response. The action of PRL on ODC activity was significantly attenuated by quinacrine, an inhibitor of PLC and PLA2 activities. These results suggest that PRL, PLA2, and PLC stimulate ODC activity via similar mechanisms in the mammary gland and make tenable the idea that the action of PRL on ODC activity may be carried out via an action of PRL on PL activity.
D000818:Animals; D004347:Drug Interactions; D005260:Female; D007700:Kinetics; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D010740:Phospholipases / Q000494:pharmacology*; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D011247:Pregnancy; D011270:Pregnancy, Animal; D011388:Prolactin / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D010738:Type C Phospholipases / Q000494:pharmacology*
D011388:Prolactin; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D009955:Ornithine Decarboxylase; D011796:Quinacrine