P-100 Prolonged exposure to polyethylene glycol (peg) 6000 severely affects the reproductive system of male Wistar rats
Authors: Ajonuma L , Bamiro S , Adeyinka R , Fapohunda D , Makanjuola S 
Published: July 2024

Abstract

Study question
Studies have shown that microplastics have adverse effects on aquatic reproductive health. Is there any potential effect of Polyethylene glycol (PEG)6000 on rodents reproductive system?

Summary answer
Despite its wide use in industry, medicine and cosmetic formulations, prolonged exposure to PEG 6000 may pose great risk, especially causing reproductive toxicity.

What is known already
The usage of Polyethylene glycol (PEG) 6000, a microplastic, is rising in industries, medicine, and cosmetic formulations. They serve as ointment bases, capsules, liquid prescription, suppositories and recently used to alleviate constipation. More so, it is one of the pivotal ingredients in soaps, detergents, and also used as chemical intermediates in textile, leather and plastic industries. Additionally, PEG 6000 is widely used in drug delivery systems and tissue engineering. Although approved for internal consumption by regulatory agencies like FDA, there are evidences of its developmental toxicity.

Study design, size, duration
Fifteen(15) rats weighing between 200-250g were used in this study. The rats were divided into three groups(A, B and C), of 5 rats in each group. Group A was designated as the control group while groups B and C were the test groups. Group A received distilled water, while groups B and C were administered 50 mg/kg and 200 mg/kg body weight of polyethylene glycol PEG6000 respectively via oral gavage daily for 6 weeks.

Participants/materials, setting, methods
After 6 weeks, the rats were sacrificed as reproductive organs and serum obtained. Enzyme immunosorbent assay (ELISA) was used for hormonal assays. Reproductive organs were weighed and tissue damage was determined using Haemoxylin /eosin staining. Antioxidant enzymes levels (Catalase, Superoxide dismutase), Glutathione peroxidise) and Lipid peroxidation (Malondialdehyde) were also evaluated. Computer-assisted sperm assay (CASA) was used to evaluate sperm parameters and sperm movement kinetics.

Main results and the role of chance
PEG 6000 caused a reduction in the weights of the rats in groups B and C when compared with control group. There was no significant change in the relative testicular and seminal vesicle organ/body weight ratio in groups B and C, however a pattern of reduction was seen in the organ/body weight ratio of epididymis and prostate, when compared to control group. Serum hormonal levels of Follicle stimulating hormone and Luteinizing hormone were reduced in the test groups when compared to control, but not significant. Testosterone was significantly reduced in groups B and C, while estradiol levels were significantly elevated in groups B and C when compared to control group. There was significant reduction in the levels of Superoxide dismutase, Catalase and Glutathione peroxidase, and a significant increase in Malondialdehyde levels in groups B and C when compared to the control group. Histopathological changes were also seen in the testes, epididymis, seminal vesicles and prostate glands of rats in the test groups. Semen analyses showed statistically significant reductions (p &lt; 0.05) in sperm concentration, motility, vitality and sperm movement kinetics of rats in the test groups when compared to the control group.

Limitations, reasons for caution
Although this study was done in rats, it may not be easy to extrapolate the present findings to humans. However, this calls for caution as primates and rodents are both members of the superorder Euarchontoglires.

Wider implications of the findings
Prolonged ingestion of PEG 6000 affects male reproductive system, alters hormonal levels, reduces sperm parameters and induces oxidative stress. Interestingly, the disruptive effects of PEG 6000 are dose-dependent, and may lead to male infertility.

Trial registration number
not applicable