Effect of estrogen on preprolactin messenger ribonucleic acid sequences.

A complementary DNA (cDNA) probe has been synthesized for rat preprolactin messenger RNA (mRNA). Following preparative gel electrophoresis, the cDNA was characterized and estimated to be approximately 75% pure. The reverse transcript is estimated to be greater than 1000 nucleotides long and, therefore, is a full-length copy of the preprolactin mRNA. It is a faithful transcript, as evidenced by back-hybridization with the mRNA. By use of the cDNA as a hybridization probe, the levels of preprolactin mRNA in the pituitary of male and female rats were monitored and found to increase following estrogen treatment. Increases in preprolactin mRNA activity, assayed by in vitro translation in the wheat germ system, were paralleled by increases in hybridization to the cDNA probe after estrogen treatment.