Effects of cholera and pertussis toxins on prolactin stimulation of lactose synthesis and ornithine decarboxylase activity in mouse mammary gland explants.
Studies indicate that G proteins are likely involved in the signal transduction pathway for prolactin's stimulation of mitogenesis in Nb2 cells. In the mammary gland, little is known about the possible role of G proteins in the prolactin (PRL) stimulation of milk product synthesis. Therefore, the effects of cholera and pertussis toxin, enzymes that modify G protein activity, were tested on several actions of prolactin on mouse mammary tissue in culture. At concentration of 0.1-0.5 micrograms/ml, cholera toxin stimulated ornithine decarboxylase activity in a dose-response fashion; when tested in concert, cholera toxin and prolactin caused an additive response. Cholera toxin by itself did not affect the rate of lactose synthesis, but at concentrations above 0.5 micrograms/ml, it attenuated the magnitude of the prolactin stimulation of lactose synthesis. Pertussis toxin (0-0.5 micrograms/ml), both by itself and in concert with PRL, had no effect on ornithine decarboxylase activity. At concentrations of 25 ng/ml and above, pertussis toxin inhibited the PRL stimulation of lactose synthesis, whereas at 0.2 and 0.5 micrograms/ml, pertussis toxin abolished the PRL response. These observations suggest that a G protein, but not Gs, may be involved in prolactin's mechanism of signal transduction in the mouse mammary gland.
Koduri
P B
PB
Department of Physiology, Wayne State University School of Medicine, Detroit, Michigan 48201.
Rillema
J A
JA
D000818:Animals; D002772:Cholera Toxin / Q000494:pharmacology*; D005260:Female; D019204:GTP-Binding Proteins / Q000502:physiology; D007785:Lactose / Q000096:biosynthesis*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D037342:Pertussis Toxin; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D010566:Virulence Factors, Bordetella; D011388:Prolactin; D002772:Cholera Toxin; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D009955:Ornithine Decarboxylase; D007785:Lactose