Age-Related Decrease of Growth Hormone and Prolactin Gene Expression in the Mouse Pituitary*

Abstract

The effects of aging on pituitary GH, PRL, and a-tubulin messenger RNA (mRNA) levels were measured in 3-, 12-, and 27-month-old male C57BL/6J mice by dot-blot hybridization. The amount of GH and PRL mRNA in the pituitary deceased dramatically with age. However, total poly(A⁺) RNA (mRNA), as measured by hybridization with radioactively labeled oligo-(dT), was not altered during aging. In addition, there were no age-related changes in the level of a-tubulin mRNA. Thus, the effects of aging on GH and PRL mRNA levels are specific; the levels of the majority of cellular mRNAs are not altered with age. GH mRNA levels decreased 35% between 3 and 12 months (P < 0.05) and a total of 75% after 27 months (P < 0.01). PRL mRNA levels decreased 65% between 12 and 27 months (P < 0.01), although there was no significant decrease before 12 months. Whereas T₃ is the most potent regulator of GH gene expression, we did not detect any significant age-related change in serum T₃ levels. These results suggest that factors other than T₃ play a role in the age-related decline in GH and PRL gene expression. (Endocrinology121: 1251–1255, 1987)