Expression of the Gene Encoding Metallothionein-3 in Organs of the Reproductive System

摘要

Metallothionein-3 (MT-3) is a newMTgene-family member that inhibits survival of rat neurons cultured in presence of brain extracts. Contrary to otherMTgenes, which are expressed in most tissues and which are highly inducible by metals,MT-3expression was reported to be mainly in the brain, and it failed to respond to metalsin vivo. We show here that MT-3 mRNA is present in several organs other than the brain, as assayed by Northern analyses. In the rat, MT-3 mRNA was detected in the testis, prostate, epididymis, tongue, ovary, uterus, stomach, heart, and seminal vesicles. The MT-3 mRNA levels in the testis, epididymis, prostate, and tongue were 22 of those in brain, while in ovary, uterus, and stomach, they were 4 of the brain level, and they were lower still in the other organs. TheMT-3gene was not inducible by CdCl2or lipopolysaccharide in rat testis and prostate. In the mouse and the human, relative MT-3 mRNA levels were lower than those found in the rat when compared with those present in brain. Testicular MT-3 transcript levels remained quite constant during rat postnatal development in animals aged from 6 to 43 days.In situhybridization analyses on human testis sections showed that MT-3 mRNA was present at different levels in both the Leydig cells and the seminiferous tubules. In orchiectomized rats, prostatic MT-3 mRNA was decreased by 75, and injections of dihydrotestosterone restored MT-3 mRNA levels to control values. Overall, these results show thatMT-3tissue-specific gene expression is broader than previously reported and provide new experimental systems to study the function and mechanism of action of the MT-3 protein.