Kallikrein gene expression in estrogen-induced pituitary tumors

Anterior pituitary kallikrein-like enzyme activity, immunoreactivity and mRNA levels have previously been shown to be regulated by estrogen, in parallel with prolactin. In this study, we have examined the relationship between kallikrein and prolactin mRNA levels in estrogen-induced pituitary tumors. Treatment of Fischer 344 rats with diethylstilbestrol implants for 3, 5 and 7 weeks produced a dramatic increase in kallikrein mRNA levels and a modest increase in prolactin mRNA levels. These changes were partially reversed by bromocriptine treatment, and completely reversed by bromocriptine plus estrogen withdrawal. Using a panel of oligonucleotide probes specific for various members of the rat kallikrein gene family, we have shown that the kallikrein-like gene expressed appears to be true kallikrein.