Do gonadotropes express growth hormone mRNA (GH mRNA)?
If GH cells retain their phenotype as they express gonadotropin mRNAs, then they may also retain the ability to express GH mRNA. Thus, we should see expression of GH mRNA by gonadotropes. This characteristic can be tested by dual labeling for GH mRNA and gonadotropin antigens with in situ hybridization histochemistry followed by immunochemistry. Ongoing studies show that expression of GH mRNA changes with the stage of the cycle. It is lowest in GH cells early in the cycle and then begins to rise. Nearly all of the GH cells express GH mRNA by proestrus. Also, there is a significant increase in expression of GH mRNA by cells with LH and FSH antigens during this rise. Counts are continuing to validate the pattern seen in the early experiments. Thus far, the hypothesis that GH cells retain their phenotype is supported by these data. The following figures show dual labeling for GH mRNA and GH antigens. The labeling for GH mRNA is in linear patches or spots distributed in the cytoplasm. The