The physiological stimulation and inhibition of release of several peptide and protein hormones appears to be associated with transcription of the respective peptide- and protein hormone-encoding genes. In the current studies we investigated whether this was also true for the rat pituitary LH system. Using an anterior pituitary primary tissue culture system, we have analyzed the effects of 10-9 m GnRH on βLH gene transcription using a transcription run-on assay, and on nuclear 0LH RNA levels using a highly sensitive solution hybridization-S1- nuclease protection assay. GnRH-stimulated release of LH does not appear to be coupled to a significant change in the rate of βLH gene transcription, but is associated with both a 2- to 3-fold increase in levels of the 0LH primary transcript and processing intermediates and a rapid decrease in the levels of fully processed βLH mRNA in the nucleus. No significant change in βLH cytoplasmic mRNA levels, however, was associated with GnRH- stimulated release of LH, in vitro. Our findings suggest that unlike several other peptide and protein hormone systems, stimulated release of βLH by GnRH in vitro is not associated with an increase in βLH gene transcription or cytoplasmic mRNA levels.