Hormonal regulation of acidic and basic fibroblast growth factor production and expression in mouse mammary gland.

Based on previous results showing developmental regulation of aFGF and bFGF, we evaluated the effect of various hormones on aFGF and bFGF mRNA levels, in mammary gland. Northern blots indicated that estrogen alone increased aFGF but had no effect on bFGF messenger RNA level. Progesterone alone increased aFGF and bFGF mRNA levels. Estrogen and progesterone together increased aFGF mRNA level in mammary gland, but the increase was no greater than that caused by either hormone alone. However, the combination of estrogen and progesterone had no effect on bFGF message level. PRL or GH, when administered with estrogen and progesterone, increased aFGF, but did not have any effect on bFGF message level. However, when PRL and GH were administered together with estrogen and progesterone, they increased bFGF messenger RNA level. Ovarian steroid withdrawal increased aFGF, but did not have any effect on bFGF mRNA accumulation. PRL alone (in the absence of estrogen and progesterone) decreased aFGF, whereas it had no effect on bFGF message level. Hydrocortisone alone decreased aFGF, but increased bFGF mRNA level. However, PRL and hydrocortisone increased aFGF, but did not have any significant effect on bFGF message level. In the overall model, during growth of the mammary gland, ovarian steroids cause an increase in aFGF mRNA. During lactogenesis, ovarian steroid withdrawal causes an increase in aFGF messenger RNA levels. Lactogenic hormones together cause a further increase in aFGF message levels.