Absence of Testicular Atrophy in Nose Only Inhalation Exposure

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

Nose-only rodent exposure systems are widely used for safety testing and experimental applications. Notwithstanding its many advantages over whole body exposure systems, the scientific community is conserned that restraint during exposure may produce stress to the animals. Stress may cause changes in the hormonal status, and coupled with confinement, may produce testicular degeneration including reduction in testicular mass, sperm motility, and mating frequency.

A recent study (Rothenberg et al., 2000) was designed to determine whether sealed nose-only exposure of the male rat causes testicular toxicity under conditions of cooling of the exposure room and appropriate acclimation to the exposure tubes. The endpoints monitored were body weight, testicular weight, sperm count, sperm motility, and histopathology of the testes, epididymides, prostate, and seminal vesicles. Thermal stress was decreased by lowering the exposure room temperature and using tail coolers (See figure below). Following acclimation, rats were exposed to filtered air for 2 hr/day for 28 days before cohabitation and continuing throughout a 14 day cohabitation period.

The authors reported that the nose only exposure in sealed tubes under the conditions of this study, did not cause adverse effects on the reproductive organs, fertility, or reproductive performance of male rats. The authors state that the study was not intended to assess acclimation and room cooling procedures as being essential to reproductive studies or whether satisfactory results could be obtained under other conditions. The study however, demonstrates that restraint of male rats in sealed nose-only inhalation exposure tubes under well-controlled conditions, following a properly designed acclimation regime, does not result in stress-related effects on male reproductive organs or in any major differences in male reproductive performance as compared to untreated controls.

Reference: Lack of Effects of Nose-Only Inhalation Exposure on Testicular Toxicity in Male Rats.  Simon J. Rothenberg,  Robert M. Parker,  Raymond G. York,  George E. Dearlove,  Margaret M. Martin,  Kevin H. Denny,  Stephen D. Lief,  Alan M. Hoberman, and Mildred S. Christian. Toxicol. Sci. 53:127-134, 2000.

 

Figure:  Above is a sealed nose-only tube with a butt plate similar to that used in the experiment.  To the right is the nose cone where the nose of the rat is exposed to the contents of the inhalation chamber.  The vertical line in the middle is the metal butt plate attached to a metal pusher which exits the black plastic stopper into the cooled room air.  

By Arlene L. Weiss, MS, DABT,  Contributing Editor

Illustration by Susan G. Shami, ScD.