Multiple and differential regulation of ovarian prolactin receptor messenger RNAs and their expression.

Three predominant prolactin receptor (PRL-R) mRNA species of 9.7, 2.1 and 1.8 kb and two minor species of 4.6 and 2.6 kb were demonstrated in the rat ovary. The long transmembrane form of the ovarian PRL-R is derived from the 9.7 kb and 4.6 kb species. The 2.6 kb species could be a variant form of this receptor with truncated or altered extracellular domain, while the 1.8 and 2.1 kb species correspond to the short transmembrane receptor form with truncated cytoplasmic domain. All five mRNA species were expressed and regulated in a developmental stage-specific manner during gonadotropin-induced ovarian maturation, luteinization and subsequent desensitization by gonadotropin treatment. Coordinate regulation of prolactin receptor binding activities and mRNA levels was observed during gonadotropin-induced heterologous up- and down-regulation of ovarian receptor sites.