Hybridization analysis of steady-state levels of uteroglobin mRNA in rabbit uterus and lung during early pregnancy.

Uteroglobin is a predominant protein in the rabbit uterus, where it is induced by progesterone, and occurs also in the lung, where its level is constitutive. A recombinant plasmid containing uteroglobin complementary DNA (cDNA) has been constructed previously from partially purified uteroglobin mRNA. In this study, the cloned uteroglobin cDNA has been used as a probe to determine the cellular content of uteroglobin mRNA at different times in early pregnancy in both rabbit uterus and lung. By RNA-excess hybridization to poly A-enriched RNA and to total nucleic acid extracts an increase in steady-state uteroglobin mRNA level was detected, from approximately 250 molecules/uterine epithelial cell in non-pregnant rabbits to approximately 6800 molecules/cell on day 4 of pregnancy, after which the levels declined progressively up to day 8. The pulmonary level of uteroglobin mRNA was about 400 molecules/cell and did not change significantly with day of pregnancy. The major factor in regulating the production of uteroglobin in the uterus of pregnant rabbits is the accumulation and subsequent depletion of its mRNA.