Unilateral Orchidectomy in Mature Cats is Not Followed by Compensatory Hypertrophy


Author's address (for correspondence): Cristina Gobello, Laboratory of Reproductive Physiology, Faculty of Veterinary Medicine, National University of La Plata. 60 & 118, La Plata CC 296 (B 1900 AVW) Argentina. E-mail: cgobello@fcv.unlp.edu.ar; cristinagobello@gmail.com


The aim of this study was to describe the effect of unilateral orchidectomy on testicular characteristics of mature domestic cats. Five, 1- to 2-year-old, cross-bred male cats were unilaterally orchidectomized on day 0 (right) and day 60 (left). The testes were processed for histological and immunohistochemical evaluation and groups compared by Student's t-test. No significant differences (p > 0.05) were found between testes groups for any of the gross (volume and gonadosomatic index) and microscopic (tubular diameters, axis, area, length and perimeter, germinal epithelium height, spermatogonias, spermatocytes, spermatids, spermatozoa, Sertoli and Leydig cells, intertubular compartment, lumen, cellular debris, tubular- intertubular proportion and basement membrane) parameters assessed. According to these biometric and morphometric results, mature cats do not develop compensatory hypertrophy within 60 days of unilateral orchidectomy.


In the domestic cat (Felis catus), surgical removal of one diseased testis is a frequent practice after unilateral trauma, neoplasm, inflammation or torsion. In addition, the use of hemicastrated animals, theoretically, offers advantages over the use of intact males in studying testicular effect of drugs as interindividual variability could be eliminated. In both clinical and research settings, the question arises whether the remaining testis suffers any post-surgery effect.

After hemicastration, compensatory hypertrophy of the remaining testis occurs in bulls (Johnson 1978), boars (Kittok et al. 1984), rams (Voglmayr and Mattner 1968) and stallions. Such hypertrophy, however, has not been detected in mice (Fawke et al. 1972). In rats, the magnitude of this response depends on the age at which hemicastration is performed (Cunningahm et al. 1978). In adult dogs, the reports are contradictory (Taha et al. 1982; Gunzel-Apel et al. 1989), while in the authors’ knowledge, there is no information concerning the effect of unilateral castration in feline species. The aim of this study was to describe the effect of unilateral castration on testicular characteristics in sexually mature cats.

Materials and Methods


Five healthy, 1- to 2-year- old, cross-bred male cats were unilaterally orchidectomized on days 0 (right testis) and 60 (left testis). The animals were exposed to more than 12 h of light per day for two months before and after the first hemicastration.

Surgery and gross examination of the testes

General anaesthesia was induced with xylazine (1–3 mg/kg IM; Kensol, Köing, Argentina) and ketamine (15–25 mg/kg IM; Ketmin-50, Holiday, Argentina) and complemented with local anaesthesia using lidocaine 1% (maximum 0.5 ml). After surgery, ketoprofen (1 mg/kg; Ketofen, Fort Dodge, Argentina) was injected SC (once) and then orally every 24 h for four additional days. This study was approved by the Faculty Institutional Care and Animal Use Committee (IACUC, Number 129/09).

Immediately after surgical removal, the testes were weighed (g) and measured [length (cm) and width (cm)] using laboratory callipers. Testicular volume (cm3) and gonadosomatic index (%; Franca and Godinho 2003) were also calculated.

Histological evaluation

The testes were longitudinally sectioned and placed in Bouin's fixative. After processing, 5-μm sections were cut and stained with haematoxylin and eosin. Microscopic images were obtained at ×10 and ×40 (Olympus BX50, Tokyo, Japan) through an attached video camera (Sony DXC 151 A CCD, Tokyo, Japan) and digitalized in a 24-bit true colour TIFF format. Fifteen to 20 tubular profiles, which were round or nearly round, were chosen randomly and measured for each animal. The maximum, minimum and medium tubular diameters (μm), major and minor axis (μm), area (μm2) and perimeter (μm) of seminiferous tubules were measured at ×10 by planimetry (Image Pro Plus, Media Cybernetics, Silver Spring, MA, USA). The germinal epithelium height (μm) was also recorded. The volume (cm3) of the testicular tissue components was determined by light microscopy using a 441-intersection grid placed on ×40 magnification. For this, 15 fields were chosen randomly (6615 points) and scored for each animal. Points were classified as one of the following: spermatogonia, primary and secondary spermatocytes, rounds spermatids, elongated spermatids, spermatozoa, Sertoli and Leydig cells, intertubular compartment, basement membrane, lumen, cellular debris and tubular–intertubular compartment proportion. The total length of seminiferous tubules (metre) was also calculated (Franca and Godinho 2003).

Sertoli cells were immunohistochemically marked (Monoclonal Mouse Anti-Vimentin Clone 9, Dako, Carpinteria, CA, USA). The EnVision System Kit (Dako, Carpinteria, CA, USA) was used as inmunohistochemical detection system. Positively stained cells showed a golden dark brown 3,3′-diaminobenzidine tetrahydrochloride–H2O2 reaction product. After counterstaining with alcoholic haematoxylin, the slides were dehydrated and mounted for examination. The cells were counted in 20 sections of tubules for each animal (Fig 1).

Figure 1.

Immunohistochemically stained Sertoli cells positive to antivimentin antibody (arrows; 40×) of the seminiferous tubules of the right (a) and left (b) testes of one of the study cats

Statistical analysis

Continuous variables of both groups (day 0 vs day 60) were analysed by Student's t-test and expressed as mean ± SEM (SPSS Inc, Chicago, IL, USA). p Values < 0.05 were considered significant.


No significant differences between testes groups were found for any of the gross and microscopic parameters assessed (p > 0.1; Table 1).

Table 1. Biometric and morphometric data of right and left testes of five hemiorchidectomized cats on days 0 and 60. No significant differences between testes were found for any of the studied parameters (p > 0.1)
ParameterRight testisLeft testis
Day 1Day 60
Testis weight (g)1.54 ± 0.41.7 ± 0.2
Testis length (cm)1.94 ± 0.11.92 ± 0.8
Testis width (cm)1.04 ± 0.11.04 ± 0.1
Testicular volume (cm3)0,95 ± 0.10,95 ± 0.1
Gonadosomatic index (%)0.03 ± 0.010.04 ± 0.01
Maximum tubular diameter (μm)240.5 ± 29.8250.8 ± 18.6
Minimum tubular diameter (μm)166.05 ± 24.4194.09 ± 13.1
Medium tubular diameter (μm)202.56 ± 26.2220.91 ± 14.9
Major tubular axis (μm)240.89 ± 29.1247.53 ± 18.3
Minor tubular axis (μm)171.88 ± 24.7200.35 ± 12.6
Tubular area (μm2)35356.15 ± 8482.839622.83 ± 5193.4
Tubular perimeter (μm)668.14 ± 84.8718.71 ± 47.7
Germinal epithelium height (μm) 58.63 ± 7.555.28 ± 5.3
Spermatogonias (cm3)0.056 ± 0.010.052 ± 0.01
Primary spermatocytes (cm3)0.10 ± 0.10.11 ± 0.1
Secondary spermatocytes (cm3)0.003 ± 0.010.002 ± 0.01
Round spermatids (cm3)0.12 ± 0.010.13 ± 0.01
Elongated spermatids (cm3)0.07 ± 0.010.066 ± 0.01
Spermatozoa (cm3)0.04 ± 0.010.03 ± 0.01
Sertoli cells (cm3)0.064 ± 0.010.072 ± 0.01
Leydig cells (cm3)0.04 ± 0.010.04 ± 0.01
Intertubular compartment (cm3)0.12 ± 0.020.12 ± 0.02
Basement membrane (cm3) 0.02 ± 0.010.02 ± 0.01
Lumen (cm3)0.2 ± 0.040.3 ± 0.03
Cellular debris (cm3)0.02 ± 0.010.01 ± 0.01
Tubular–intertubular proportion7.17 ± 1.27.29 ± 1.3
Total tubular length (m)38.73 ± 10.532.66 ± 6.2
Sertoli cells per seminiferous tubule 27.7 ± 1.827.7 ± 1.8


To our knowledge, this is the first investigation to describe the effect of hemicastration in domestic cats providing a background for comparative studies not only with other felids, but also with other mammals. According to these biometric and morphometric results, adult cats, the same that mice (Fawke et al. 1972) and rats (Cunningahm et al. 1978), do not seem to develop compensatory hypertrophy after hemiorchidectomy. Furthermore, weight, gonadosomatic index and tubular diameter in both testes groups were in accordance to what has been previously reported for the species (Franca and Godinho 2003). Different study designs, reproductive maturity of the animals and end points measured might explain different responses to the unilateral orchidectomy among mammals.


This study was partially financed by PIP 0001 (CONICET). GGR and CG are Research Fellow and Career Scientist, respectively, of National Research Council (CONICET) of Argentina.

Conflicts of interest

None of the authors of this paper have a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.