Expression of LH receptor mRNA. A. Semi quantitative RT-PCR analysis (using GAPDH as an internal control) of LHR mRNA in +/+ (black bars) and -/- (hatched bars) ovaries at 0.5, 1.5, 2.5 and 3.5 day post coitum (d.p.c.); upper panel, inverse picture of ethidium bromide stained agarose gel shows a typical RT-PCR reaction; lower panel, bars, means ± SEM of the densitometric analysis (n = 6 for each stage). B. In situ hybridization of LHR in ovarian sections at 2.5 d.p.c. of PRLR+/+ and PRLR-/- mice. The predominant source of LHR expression is within cells of corpora lutea. A representative section is shown at low-power magnification in bright field (above) and dark field (below) to demonstrate the histology and highlight the hybridization signal, respectively. In the absence of the PRLR, expression of LHR (arrows) is no longer seen in corpora lutea but is seen in the theca cells and in the interstitial cell population. Negative control sections probed with sense riboprobes showed no defined pattern of probe hybridization (data not shown).