Acute effects of styrene inhalation on the neuroendocrinological system of rats and the different effects in male and female rats

Abstract

There have been several epidemiological and experimental studies about styrene from the neuroendocrinological viewpoint. Some reported that styrene exposure affected the neuroendocrinological system and enhanced prolactin (PRL) secretion, but others have denied those effects. It was assumed that styrene exposure caused depletion of dopamine (DA), which is a PRL inhibitor, and that, in consequence, the PRL level increased. However, not only DA but also many other factors control PRL secretion. Therefore, the mechanism of hypersecretion of PRL has not yet been clearly elucidated. In addition, effects of styrene on the female reproductive system have been reported, but the susceptibility needs to be further studied. Therefore, to investigate what causes hypersecretion of PRL and how different the susceptibility is in males and females, we studied acute effects of styrene exposure on the neuroendocrinological system in male and female rats. Immediately after exposure to 150 ppm styrene vapor for 10 days (8 h/day), male and female rats were killed, and blood and brain samples were collected. The styrene concentration in blood, hormones such as PRL, growth hormone (GH) and thyroid-stimulating hormone (TSH) in plasma and neurotransmitters in various brain regions were measured. The styrene concentration in the blood of female rats was higher than that in male rats, and the PRL level was significantly increased in female exposed rats compared with controls. No significant change was observed in male rats. We did not observe any significant changes in DA, 5-hydroxytryptamine (5-HT) or their metabolites. Because neurotransmitters were not affected in either male or female rats, the mechanism enhancing PRL secretion remains unclear. These results suggest that styrene exposure may cause hypersecretion of PRL and that the sensitivity to styrene exposure of the female may be higher than that of the male.

Evaluation of potential health effects associated with occupational and environmental exposure to styrene – an update

“…The only known physiological function of prolactin is the stimulation of milk production and many normal stress situations may lead to elevations without any chemical exposure (Theorell et al 1990). Although screening or guideline studies do not exist for experimental verification of the human observations, mechanistic studies in animal on dopamine, the prolactin-regulating neurotransmitter, do not support an explanation of how styrene may affect prolactin levels (Gagnaire et al 2006;Jarry et al 2002;Umemura et al 2005). Therefore, given the lack of a plausible mechanistic explanation, coupled with the nature of the changes, unspecific acute workplace-related stress is a possible alternative explanation to styrene exposure in these workers.…”

OP Pesticides, Organic Diets, and Children’s Health: Lu et al. Respond

“…In fact, prolactin can be increased by exposure to lead (Govoni et al 1987;Lucchini et al 2000), organic mercury (Carta et al 2003), and manganese (Ellingsen et al 2003;Smargiassi and Mutti 1999;Takser et al 2004), but it can be decreased by exposure to inorganic mercury Lucchini et al 2003;Ramalingam et al 2003), alluminum (Alessio et al 1989), and cadmium (Calderoni et al 2005;). Subjects exposed to chemicals such as styrene (Bergamaschi et al 1996;Luderer et al 2004;Umemura et al 2005), perchloroethylene (Beliles 2002;Ferroni 1992), and anesthetic gases (Lucchini et al 1996;(Marana et al 2003) have shown an increase of serum prolactin, whereas polychlorinated biphenyls (De Krey et al 1994) Possible mechanisms, other than direct effects at the cellular level, may be related to different neurotransmitters involved in the modulation of prolactin secretion. For example, the dopaminergic and serotoninergic systems, respectively, are involved in the physiologic regulation of this hormone as a tonic inhibitor and as an excitatory modulator.…”

Thyroid Function and Exposure to Styrene

“…Increases in serum growth hormone and TSH were also observed and were associated with biomarkers of styrene exposure (13)(14)(15)(16). Toxicological studies on rats also support prolactin secretion as a styrene target, with sex-related differences (17). An up-to-date, comprehensive review of health effects and exposure to styrene is available (18).…”