EFFECTS OF TOXIC LEVELS OF LEAD ON GENE-REGULATION IN THE MALE AXIS -INCREASE IN MESSENGER RIBONUCLEIC-ACIDS AND INTRACELLULAR STORES OF GONADOTROPHS WITHIN THE CENTRAL-NERVOUS-SYSTEM
D. Klein et al., EFFECTS OF TOXIC LEVELS OF LEAD ON GENE-REGULATION IN THE MALE AXIS -INCREASE IN MESSENGER RIBONUCLEIC-ACIDS AND INTRACELLULAR STORES OF GONADOTROPHS WITHIN THE CENTRAL-NERVOUS-SYSTEM, Biology of reproduction, 50(4), 1994, pp. 802-811
Lead is a male reproductive toxicant. Lead exposure results in a gener
al suppression of the hypothalamic-pituitary-testicular (HPT) axis in
male rats. The mechanism(s) for this disruption by lead is unknown. To
xic lead levels seem to disrupt central nervous system (CNS) control o
f the HPT system, resulting in a decrease in serum testosterone levels
and sperm concentrations. A study designed to elucidate the mechanism
s accounting for the disruption of the normal function of the male axi
s by toxic lead levels at the molecular level demonstrated a 2-3-fold
enhancement of mRNA levels of GnRH and the tropic hormone LH. A 3-fold
increase of intracellular stores of LH was also found. Because mRNA l
evels of LH and GnRH and pituitary levels of stored LH are proportiona
l to blood levels of lead, we hypothesize that lead interferes with th
e normal release of tropic hormones and disrupts hormonal feedback mec
hanisms. The observed pleiotropic effects of lead upon the male axis a
nd other systems may be explained by simple and unique competition by
lead with normal metal ion binding sites that govern genetic control o
f specific genes.