Time‐dependent effects of lead on rat reproductive functions

Abstract

The effects of exposure to lead on endocrine function and the reproductive parameters were studied in pubertal rats treated with 1.0 g l-1 lead acetate in drinking water for 20 days (subacute group) or 9 months (chronic group) in addition to i.v. injections of lead acetate (0.1 mg 100 g-1 body wt.) every 10 (subacute group) or 15 days (chronic group). Although basal levels of testosterone were higher both in plasma and in testes of acutely intoxicated animals, the circulating levels of luteinizing hormone (LH) were not affected in either group, nor was the LH-releasing hormone content of the median eminence. The density of [125I]LH/human chorionic gonadotrophin (hCG) binding sites in testicular homogenates was reduced by saturnism in both groups, concomitant with a significantly increased apparent affinity constant of the hormone-receptor complex. These data can be viewed as the result of a mixture of specific lead toxicity (e.g. at the enzyme level) with other more general actions (e.g. at the level of the hypothalamus-pituitary-testicular axis).

Antiestrogenic activity of lead

“…ferent and sometimes opposite uterine eosinophilia from those caused by lead administration 24 h before hormone treatment are in agreement with the report Ž . by Kempinas et al 1994 on time-dependent differences between the different effects of lead on reproductive changes. The slight tendency for a decrease in ( Bars indicate means expressed as percent of maximal ) response to estrogen plus or minus standard error of the mean.…”

“…Exper-imental studies suggest that lead affects female reproductive organs through different mechanisms. The Ž heavy metal may interact at the enzyme level Kempinas et al, 1994 . It may interfere with the action of reproductive hormones at the target organ by modifying the activity of estrogen receptors in Ž .…”

Long-term, low-dose lead exposure alters the gonadotropin-releasing hormone system in the male rat.

“…Lead exposure is associated with neurologic (3-6), growth (3,7), and reproductive defects (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25). Lead exposure in men has been associated with abnormalities of spermatogenesis (9,(11)(12)(13)).…”

“…Increasing the length of exposure to 8 weeks seems to allow the adult animal to normalize its responses (22). Other data suggest that the lead-exposed animal is able to adapt to the metal's toxic effects (20,(22)(23)(24)(25).…”

Effect of Prenatal Exposure to Lead on Estrogen Action in the Prepubertal Rat Uterus

“…Among them, changes may occur at the enzyme levels [10, 11] or in the action of sex steroid hormones themselves, mainly estrogens, in the uterus [12–14]. The interaction of lead with hormone action may be direct, via qualitative or quantitative changes in hormone receptors [15], or caused by changes in levels of other hormones that modify the action of sex steroids, such as glucocorticoids [16] and prolactin [17], hormones that increase under the effect of exposure to lead [18].…”