Lack of Effects of Nose-Only Inhalation Exposure on Testicular Toxicity in Male Rats

Abstract

Reductions in testicular mass, sperm motility, and mating frequency have been attributed to the stresses caused by confinement of Sprague-Dawley male rats in nose-only inhalation exposure tubes. Testicular changes, including an increase in testicular atrophy, have been detected at an increased incidence in male rats used in inhalation studies as compared with rats of the same age and strain used in oral toxicity studies. This study was designed to determine whether nose-only exposure of male rats caused testicular toxicity under conditions of cooling of the exposure room and appropriate acclimation to the exposure tubes. In order to acclimate the rats to the nose-only inhalation exposure apparatus, all male rats were placed in the exposure tubes for at least four successively increasing time intervals (15, 30, 45, and 60 min) on 4 separate days, with a rest period of approximately 48 h between the first and second acclimation. Twenty male rats were exposed nose-only to filtered air for approximately 2 h per day for 28 days before cohabitation and continuing throughout a 14-day cohabitation period. To reduce thermal stress, the exposure room temperature was maintained at 64 to 70 degrees F. Twenty control rats were housed in the same room as the exposed rats but were not placed in exposure tubes. End points monitored were body weight, testicular weight, sperm count, sperm motility, and histopathology of the testes, epididymides, prostate, and seminal vesicles. The control rats gained weight more rapidly than the exposed rats. All the rats in both groups mated successfully, and testicular weights, normalized to body weight, were similar for both groups. More importantly, there were no microscopic changes that could be considered an adverse effect on the reproductive tissues in the male rats placed in exposure tubes. Thus, nose-only exposure for up to 2 h per day for a total of 42 days did not cause adverse effects on the reproductive organs, fertility, or reproductive performance of male rats under the conditions of this study.

Evaluation of toxicity of aerosols from flavored e-liquids in Sprague–Dawley rats in a 90-day OECD inhalation study, complemented by transcriptomics analysis

“…7). Tubular degeneration and epididymal changes attributed to the injury caused by the confinement of rats in nose-only inhalation exposure tubes were consistent to procedure-related effects described in the literature (Rothenberg et al 2000). Therefore, subtle changes in testis weights could not be concluded as a nicotine effect reported previously for orally or subcutaneously administered nicotine (Aydos et al 2001;Oyeyipo et al 2010); however, the testicular degeneration is consistent with the phenomenon reported for restrained rats, even in controls for inhalation exposure (Lee et al 1993).…”

Inhalation Exposure to Carbon Nanotubes (CNT) and Carbon Nanofibers (CNF): Methodology and Dosimetry

“…These investigations demonstrated convincingly a retardation of body weight gain, even in air-exposed controls, as evidenced by a rise in body weight in the postexposure phase immediately following the termination of subchronic or chronic tube exposures ( Figure 6 ). Rothenberg et al (2000) found that even short daily nose-only tube exposures of rats to air for 42 d resulted in a 24% lower body weight, although no adverse effects on testes or reproductive performance was found. Pauluhn and Mohr (1999) confirmed this effect of nose-only exposure on body weight reduction in a 4-wk study in rats.…”

“…The former requires individual placement of rodents in compartmentalized areas in order to avoid huddling of the animals and permits some free movement, whereas their movement is severely restricted by placing them in narrow tubes during nose-only exposure with the noses protruding into the plenum with continuously supplied aerosol. This induces significant stress in the animals ( Phalen 2009 ), as evidenced by a retarded body weight gain during longer term nose-only exposures ( Coggins et al 1993 , 2011 ; Pauluhn and Mohr 1999 ; Rothenberg et al 2000 ). In contrast, contamination of the fur by aerosolized materials is restricted to the head and perhaps shoulder area, whereas during whole-body exposure aerosol deposition occurs on the whole-body surface area, resulting in some additional gastrointestinal (GI) tract exposure due to preening (see more discussion under “Types of Inhalation”).…”

“…Surrounding room air might be sufficient to aid cooling of rats. Rothenberg et al (2000) suggested room air temperature of 64–70°F to reduce thermal stress during nose-only exposures.…”

LC50 Determination of tert-Butyl Acetate using a Nose Only Inhalation Exposure in Rats

“…Decreased body weight gains were observed on day 2, but they did not show a doseresponse relationship and normal body weight gain was restored on day 7. The difference was presumed to be related to the additional stress of handling and placement of rats in the exposure tubes and the additional time spent away from the feed containers (Rothenberg et al, 2000) .…”