Histomorphology of testis
From the present findings, it could be observed that the development of the process of spermatogenesis was different in zinc-supplemented group of rats when compared with that of control rats. Histomorphological studies of the seminiferous tubules of the testes revealed that at 6 weeks of age, the tubules were compactly arranged in all the treatment groups (control, T1 and T2) of rats (Fig 1, Fig 2 Fig 3). In all the three groups, the seminiferous tubules had distinct lumina. While elongated spermatids were visible in the seminiferous epithelium only in treatment (T1 and T2) groups, more concentrations of the same being noticed in T1 group (Fig 4); no spermatozoa could be located in the same site in the control rats. The developmental difference in the process of spermatogenesis in the treated group could be attributed to function of zinc because zinc is an important mineral for normal testicular development and maintenance of germinal epithelium
(Anderson et al., 1993) and it is vital for spermatogenesis process
(Davies, 1985). Spermatogenesis process in the male is impacted by dietary zinc levels
(McDowell et al., 1993). It acts as a cofactor for several enzymes which help in steroidogenesis processes in the body. Impairment of spermatogenesis could be attributed to the direct action of zinc on testes or indirectly from Leydig cell degeneration indicating that zinc is a critical component for maintenance of both mitotic and meiotic stages of spermatogenesis. Other workers
(Abdella et al., 2011; Omu et al., 2015) also found zinc supplementation in diet of rats resulted remarkable improvement of spermatogenesis.
Al-Ani et al., (2015) studied the protective influence of zinc on reproductive parameters in male rats treated with cadmium and they found that testicular sections of the control group showed seminiferous tubules with normal germ cell population layer thickness with a normal orderly arranged pattern up to mature spermatid and no malignant or abnormal cell was seen within the germinal epithelium, whereas, in cadmium treated group, sections showed a decrease in thickness of germ cell layer, widening of the central seminiferous tubules lumen and prominent germ cell population necrosis. In the group treated with cadmium and zinc, sections of tubules showed recovery of germ cell population, normal germinal epithelium thickness and diameter with orderly arranged germ cell up to spermatid with adequate Sertoli and Leydig interstitial cells population. However, when the effect of lipid-zinc interaction was studied in testis of mice
(Taneja et al., 1995) it was observed that the testis in low lipid-zinc deficient diet, low lipid-zinc supplemented and high lipid-zinc supplemented groups did not display any abnormality in the germ cell population of the seminiferous tubules.
At 8 weeks of age, the seminiferous tubules were more organized than the previous age in all the three treatment groups (control, T1 and T2). The seminiferous tubules were separated forming well developed interstitial tissues which were more marked in T1 (Fig 5) as compared to the control and T2 groups (Fig 6) of rats. Sperm cells were seen adhering to the apical surface of the seminiferous epithelium and in its lumen in all the rats of T1 group (Fig 7). Again, in few of the rats of T2 group, sperm cells were seen adhering to the apical surface of the seminiferous epithelium and in its lumen however no such cells were visible in the rats of control group. The maximum number of spermatozoa seen in the seminiferous tubular lumen in the T1 group (Fig 7) as compared to T2 treatment group at 8 weeks could be ascribed to higher beneficial effect of zinc @ 50 mg/kg body weight in influencing the testicular function of spermatogenesis as it was also reported earlier by
Egwurugwu et al., (2013) that oral zinc supplementation within tolerable level has beneficial effect.
Turgut et al. (2003) observed that following high doses of zinc supplementation had degenerative changes including spermatic arrest, degeneration of seminiferous tubules and fibrosis in interstitial tissues and this could significantly alter sperm motility.
At the age of 10 weeks, the seminiferous epithelium of the rats of all the control (Fig 8), T1 (Fig 9) and T2 (Fig 10) groups showed spermatozoa in the lumen of the seminiferous tubules. Similar histological features in the testis of rats of the control, T1 (Fig 11) and T2 was seen at 12 weeks of age, however, the concentration of spermatozoa was seen more in the lumen of the seminiferous tubules as compared to the previous age in all the rats under study. In other studies
(Campion et al., 2013) sperms were detected in the caput, corpus and cauda epididymis in 45, 49 and 49 days after birth, respectively and the sperm count increased after 91 days of birth in male Wistar Han and Sprague-Dawley rats.
Histomorphology of Epididymis
Histomorphological studies revealed no sperm pack in cauda epididymis in all group rats at 6 weeks of age in the present investigation. However, at 8 weeks of age, the sperm pack was seen in the lumen of the epididymal tubules of the cauda epididymis of T1 (Fig 13) and T2 (Fig 14) groups but it was not seen in control (Fig 12) rats. The significant finding was that in T1 rats, the sperm pack was very compact at 10 weeks (Fig 15) onwards in cauda epididymis as compared to the control (Fig 16) and T2 (Fig 17) group of rats. This clearly suggested that the zinc supplemented rats had received intrinsic stimulatory effect, most likely from zinc, on spermatogenesis to cause early appearance of male germ cells in the epididymis.
McDowell et al., (1993) also stated that spermatogenesis and the development of primary and secondary sex organs in male are impacted by dietary zinc level. Further the present study showed that sperm pack in T1 group rats had more concentration of sperms as compared to the T2 group rats which might be due to beneficial effect of zinc @ 50 mg/kg body weight over dose rate of 100 mg/kg body weight per day.
