Testis response to low doses of cadmium in Wistar rats

Abstract

Although it is well known that cadmium (Cd) causes adverse effects on male rat reproductive organs, few studies have quantified alterations caused by its low doses. Quantification of these alterations, especially in the testis, was measured using morphometry. A single dose of cadmium chloride (1 or 1.2 mg/kg BW) was injected i.p. in adult rats, killed after 7 or 56 days. The lower dose caused slight alterations as measured by morphometrical analysis. The higher dose caused significant reduction in testis and epididymis weight, gonadossomatic index and length of seminiferous tubule (ST) after 7 and 56 days. Cadmium significantly reduced the ST diameter after 56 days. Decreased volume density of ST, after 7 and 56 days, was accompanied by an increase in interstitium volume density. The damage caused by the dose of 1.2 mg/kg can be clearly observed with light microscope. After 7 days, the tubule lumens were filled with degenerated germ cells and multinucleated spermatid aggregates. Vacuolization of the seminiferous epithelium was also observed. After 56 days, increased damage resulted in vacuolated ST, consisting only of Sertoli cells. Scanning electron microscopy examination of the testis showed that, in the group cadmium treated (1.2 mg/kg) and killed after 56 days, the interstitial tissue presents a compact and fibrous appearance with absence of fenestrae. The seminiferous epithelium height diminished and the absence of spermatozoa can be noted. The results show that a very small difference of Cd dose causes a sudden increase in testicular damage, apparently overpowering this tissue's natural defences.

Figure 1

Light microscopy of a control rat testis and under the effect of cadmium. The seminiferous tubules (ST) are well preserved in the controls (a: 7 days and b: 56 days) and in rats treated with cadmium 1 mg/kg BW (c: 7 days and d: 56 days). Rats treated with cadmium 1.2 mg/kg BW (e) exhibit degenerated seminiferous tubules with multinucleated spermatid aggregates with apoptotic nuclei, after 7 days. Note the reduced tubular diameter, absence of lumen (lu) and the thick, fibrous interstitium (IN). After 56 days (f), the progressive damage resulted in seminiferous tubules lined only by Sertoli cells. Multinucleated spermatid aggregates with apoptotic nuclei and Sertoli cells are indicated by white and black arrows respectively. Blood vessels (v). Fluid space (Star). Vacuolization (Arrow head). Scale bars: 50 μm.

Figure 2

Scanning electron microscopy of control rat testis and under the effect of cadmium after 56 days. (a) Testicular parenchyma shows a delicate lattice with large fenestrae of interstitial tissue. The seminiferous tubules are well preserved in the control group. A large space for fluid was observed between the interstitial tissue and the seminiferous tubules. (b) Detail of the seminiferous tubule with intact epithelium and the presence of spermatozoa in the lumen. (c) In cadmium (1.2 mg/kg BW) treated group, the interstitium shows a dense fibrous aspect with few fenestrae and reduced fluid space (white star). (d) The reduced epithelium height and vacuolization is observed in the seminiferous tubules. Note the absence of spermatozoa in the lumen. The fluid space was diminished or not clearly observed. Blood vessels (v) have thicker walls. White and black curved arrows: fenestrae. Scale bars: a, c, d: 100 μm; b: 10 μm.