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Effects of the adsorption behavior of polyamide microplastics on male reproductive health by reduction of testosterone bioavailability

Microplastics (MPs) are global environmental pollutants with potential toxicity concerns, and their effects on the reproductive system have attracted increasing attention. This study investigated the interaction between MPs and mammalian biomolecules, focusing on the relationship between the testosterone adsorption behavior of MPs and male reproductive health. The adsorption capacity of different types of MPs for testosterone was evaluated in vitro experiments. Polyamide (PA)-MPs exhibited stronger adsorption, while polymethyl methacrylate (PMMA)-MPs displayed the weakest adsorption. Sorption equilibrium between PA-MPs and testosterone was achieved within 6 h, fitting the Pseudo-2nd-order model and Langmuir isotherm. The effects of MPs on male reproduction in mice was determined in vivo experiments. Male mice were treated with 0.1 and 0.5 mg/d PA-MPs/PMMA-MPs by gavage once per day for 28 days. The results showed that only 0.5 mg/d PA-MP exposure induced decreased serum testosterone levels, increased testicular testosterone levels compared to the control, and more severe damage to seminiferous tubule structure, sperm motility and sperm morphology compared to the PMMA-MPs group. Meanwhile, PA-MPs could reduce intracellular nuclear translocation of androgen receptor (AR) mediated by testosterone, while PMMA-MPs had no impact. The study revealed that PA-MP adsorption reduced testosterone bioavailability and caused sperm quality to decline, offering new insights into the combined toxicity mechanism of MPs in male mammals.

Structure-dependent retention of steroid hormones by common laboratory materials

The tendency of steroid molecules to adsorb to various materials, particularly plastics, has been known of for decades but has not received widespread attention in the scientific community, and a modern, systematic study is lacking. This adsorption is an important consideration for researchers working with steroid hormones as it could skew the results of various experiments. Here we show that steroids adsorb to various vessels used in experiments, including microcentrifuge tubes, glass vials, and cell culture plates, in a manner that depends on the steroid's molecular structure and on the type of vessel. The lipophilicity of steroids is a strong predictor of the degree of adsorption, with nearly 50 % of the most lipophilic steroid tested, pregnenolone, retained in a high-adsorbing microcentrifuge tube after one hour incubation of an aqueous pregnenolone solution followed by removal of the aqueous solvent. We also show the effects of other factors such as incubation time, centrifugation, and temperature on adsorption, and show that adsorption can be mostly prevented by the presence of serum proteins in steroid solutions and/or by the use of low-adsorbing tubes.

On the stability of salivary progesterone under various conditions of storage

The concentrations of progesterone in saliva of women exhibited significant decreases when the fluid was stored in plastic vials for 3 days at room temperature or 37 C. The addition of antibiotics or a variety of metabolic poisons to the saliva prior to storage did not prevent the progesterone decrement. However, the addition of albumin (2 g/dl) was protective, suggesting that the protein impeded adsorption of salivary progesterone by the plastic container. Saliva could be maintained at 37 C for 3 days in glass vials or at -20 C in plastic containers for indefinite periods without loss of progesterone titers. These data indicate that a patient under luteal function assessment may collect saliva samples in glass vials at regular intervals during the latter half of her cycle and store them in the freezer compartment of the refrigerator until shipment by mail to the laboratory for progesterone assay. With special care, plastic vials charged with albumin may also be used.

Adsorption of pregnanediol-3 alpha-glucuronide by plastics and glass

Radioactive pregnanediol-3 alpha-glucuronide at low concentration was found to bind to a number of common laboratory materials. Adsorption was greatest with polypropylene and unsilanised glass tubes. The presence of 0.1% gelatine reduced adsorption, except in polyethylene insert vials. Adsorption of pregnanediol-3 alpha-glucuronide may present a problem in radioimmunoassay studies.

Solubility parameter, specific molar cohesion, and the solubility of ethylene oxide in polymers

The polarity of polymers is commonly characterized by their solubility parameter to describe their interaction with small molecules or by their specific molar cohesion to describe interchain attraction. A linear relation between these two parameters is demonstrated. Ethylene oxide (EO) is used to sterilize containers and devices containing plastics or elastomers. The solubility parameter concept is applicable to the sorption of EO by such polymers provided crystallinity and rubbery/glassy state are taken into account. The delta value of EO, calculated from the temperature dependence of its vapour pressure, is 10.8 (cal/cm3)1/2. The highest EO solubility is in polyvinyl chloride and polycarbonate, whose solubility parameters match that of EO closely. The solubility in other polymers decreases as their solubility parameters diverge increasingly from 10.8. At comparable delta values, polymers in the rubbery state dissolve 6000 to 8000 ppm EO more than polymers in the glassy state. EO solubility in the amorphous fraction of polymers above their glass transition temperatures ranges from 20 800 ppm for plasticized polyvinyl chloride (delta = 9.2) to 800 ppm for polytetrafluorethylene (delta = 6.2).

Studies in porphyria. I. A defect in the reductive transformation of natural steroid hormones in the hereditary liver disease, acute intermittent porphyria

A variety of 5beta steroid metabolites derived from hormones natural to man are potent inducers experimentally of delta-aminolevulinate synthetase, the rate-limiting enzyme in porphyrin-heme formation. This mitochondrial enzyme is found at high levels of activity in the livers of patients with the genetic disease, acute intermittent porphyria (AIP). In this study the metabolism of (14)C-labeled testosterone was examined in AIP patients to determine whether there was a disproportionate conversion of the hormone to its 5beta, compared to its 5alpha metabolite. The results indicate that AIP subjects do generate a substantially greater than normal fraction of 5beta metabolite from this steroid; the excessive degree of ring A reduction of testosterone taking place via the 5beta pathway in the porphyric patients averages 350% greater than in the nonporphyric subjects. In one asymptomatic AIP patient the disproportionate generation of 5beta metabolite from the hormone reached a level 10 times the normal mean. Studies with a second (14)C-labeled hormone, dehydroisoandrosterone, whose metabolism in man resembles that of testosterone, confirmed the derangement in reductive transformation of steroids found in the individuals carrying the genetic lesion of AIP. These findings define a new endocrine abnormality in AIP patients and raise the possibility that endogenously derived 5beta steroids may contribute by an induction mechanism to the increased levels of hepatic delta-aminolevulinate synthetase activity found in AIP patients.

Sites of in vivo extraction and interconversion of testosterone and androstenedione in dogs

The interconversion and extraction of testosterone and androstenedione across and within different tissues or areas have been studied by the constant infusion technique. The results were calculated using the (3)H/(14)C ratios and radioactive concentrations of testosterone and androstenedione obtained from afferent and efferent blood and tissues at equilibrium. In each tissue studied, the interconversion between testosterone and androstenedione inside the tissue was significantly higher than the corresponding interconversion across the tissue. The pulmonary contribution to the total interconversion between testosterone and androstenedione was far more important than that of any of the other tissues studied. The hepatic metabolic clearance rates of testosterone and androstenedione were not different from their metabolic clearance rates in the mesenteric area. The extraction of each of these compounds, although not negligible, was lower in the kidney and the femoral bed compared with the extraction in the liver and the mesenteric area. Finally, with the possible exception of the liver, testosterone and androstenedione were more completely metabolized when they originated from the cells than from afferent blood. The evaluation of these different tissue transfer constants provides more precise information concerning the relative importance of different sites in the metabolism of these interconverting hormones.

Metabolism of testosterone and androstenedione in normal and ovariectomized women

Metabolic clearance rates of testosterone (MCR(T)) and androstenedione (MCR(A)) were determined twice during the same cycle in six normal women, using a constant infusion of testosterone-(3)H and androstenedione-(14)C. Nonlabeled steroids served as internal standards. Plasma concentrations of testosterone (i(T)) and androstenedione (i(A)) were measured, and the blood production of testosterone (P(B) (T)) and of androstenedione (P(B) (A)) were calculated. The interconversions of these two steroids were also estimated. Six ovariectomized women were studied in the same manner. For testosterone, the mean i(T) in the normal women was not significantly different from that in the ovariectomized subjects, whereas the MCR(T) and P(B) (T) were significantly lower in the ovariectomized subjects. For androstenedione, the mean MCR(A) values of the two groups of subjects were not different, whereas the i(A) and P(B) (A) in the normal women were about double those in the ovariectomized subjects. In comparing the follicular and luteal phases of the menstrual cycle in four of six subjects there was no difference in i(T), MCR(T), or P(B) (T), whereas i(A), MCR(A), and P(B) (A) were increased in the luteal phase. In one ovariectomized woman infused with testosterone and androstenedione at physiologic levels, MCR(T) doubled but MCR(A) remained the same. After six wk on estrogen, the same subject did not show any change in MCR(T) after infusion of testosterone. It is suggested that MCR(T) depends on P(B) (T) and on plasma binding of testosterone which is partly estrogen dependent.

Testosterone and androstenedione blood production rates in normal women and women with idiopathic hirsutism or polycystic ovaries

The average plasma testosterone concentration of women with either hirsutism or polycystic ovaries and hirsutism was higher (p < 0.01) than that of normal women although the ranges overlapped. Testosterone blood production rates averaged 830 +/- 120 SE and 1,180 +/- 310 SE mug per day in the two groups of hirsute women and 230 +/- 33 SE mug per day in normal women. The ranges did not overlap. The testosterone metabolic clearance rates of hirsute women (1,090 +/- 140 SE L per day) and of men (1,240 +/- 136 SE L per day) were significantly higher than those of normal women (590 +/- 44 SE L per day). These differences persisted when the metabolic clearance rates were corrected for surface area. We suggest that testosterone metabolic clearance rates vary directly with some function of testosterone production. The mean plasma androstenedione levels (2.8 +/- 0.35 SE and 2.8 +/- 0.30 SE mug per L) and production rates (6,060 +/- 450 SE and 7,360 +/- 345 SE mug per day) of the women with hirsutism or polycystic ovaries, respectively, were significantly higher than those of normal women (1.5 +/- 0.22 SE mug per L; 3,300 +/- 830 SE mug per day). The androstenedione metabolic clearance rates were the same in each group. Plasma androstenedione was the precursor of 49% of plasma testosterone in normal women and of 26% of plasma testosterone in hirsute women. Thus, 74% of the plasma testosterone in these subjects must have been either secreted or derived from a precursor that did not enter the plasma androstenedione pool.