Ovarian ornithine decarboxylase regulation in the immature, the pubescent, and the pseudopregnant rat.
Ovarian ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) regulation was investigated in immature, pubescent, and pseudopregnant rats. After initial induction of the enzyme by injection of lutropin in the immature rat, continued daily injections resulted in a graded decrease in the activity of the enzyme. In the 32-day-old rat, the induction and subsequent decline in enzymic activity after a single injection of lutropin could only be partially reversed by injections of the hormone at 4-hr intervals. This decrease could not be attributed to a decrease in ovarian in vivo uptake of the hormone. In the pseudopregnant rat, ovarian ornithine decarboxylase is highly refractory to induction by either a single injection or repeated injections of lutropin. This refractoriness occurs despite a 2- to 3-fold increase in ovarian in vivo uptake of the hormone compared to that in the 32-day-old rat. It is suggested that the refractoriness observed with all three tissues is a function of cell differentiation.
D000818:Animals; D001692:Biological Transport; D002262:Carboxy-Lyases / Q000378:metabolism*; D002454:Cell Differentiation; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D007986:Luteinizing Hormone / Q000378:metabolism / Q000494:pharmacology; D009955:Ornithine Decarboxylase / Q000378:metabolism*; D010053:Ovary / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D011555:Pseudopregnancy; D051381:Rats; D012741:Sexual Maturation; D013347:Subcellular Fractions / Q000378:metabolism
D007986:Luteinizing Hormone; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase