Male reproductive functions are controlled by different hormones notably LH, FSH, estrogen and testosterone . The plasma activities of these hormones are a function of the hypothalamo-pituitary–testicular axis which is initiated by the pulsatile release of gonadotropin releasing hormone from the hypothalamus . This, in turn, stimulates the secretion of anterior pituitary trophic hormones, with LH acting on the testicular and Leydig cells for steroidogenesis and FSH acting on Sertoli cells for spermatogenesis . Result obtained from this study showed a significant decrease (p < 0.05) in plasma concentrations of FSH, LH, testosterone and estrogen (2.64 ± 0.63, 1.90 ± 0.82, 2.33 ± 0.24, and 13.29 ± 1.80, respectively) in rats fed on cotton seed when compared with values obtained in the control rats (3.80 ± 0.25, 2.60 ± 0.16, 3.80 ± 0.28, 25.11 ± 0.78) and aqueous Cissus populnea suspension-fed rats (4.47 ± 0.33, 3.01 ± 0.10, 3.94 ± 0.16, and 27.72 ± 1.16, respectively) (Table 1). These findings corroborate report from similar studies where animals fed on cotton seed showed a significant reduction in serum level of estrogen, FSH and LH [24, 25]. Meanwhile, improvements were observed in the concentrations of these hormones following administration of aqueous Cissus populnea suspension after initial cotton seed meal with values of 3.32 ± 0.44, 2.41 ± 0.61, 2.50 ± 0.43, and 17.91 ± 1.51, respectively, for FSH, LH, testosterone and estrogen as compared to 2.64 ± 0.63, 1.90 ± 0.82, 2.33 ± 0.24, and 13.29 ± 1.80, respectively, observed in rats fed on cotton seed only (Table 1). This corroborates reports from similar studies involving aqueous Cissus populnea root [26, 27] but is in contrast to others . Cotton seed oil consumption has been implicated in the induction of infertility in human as it is rich in gossypol which have contraceptive effects and by decreasing sperm concentration, motility, and viability [28,29,30]. The observed ameliorative effect of aqueous Cissus populnea suspension on hormonal parameters may be due to exhibition of gonadotrophic activities by certain phytochemicals therein present on the pituitary gland thereby enhancing spermatogenesis and reproductive processes . The significant decrease in plasma FSH, LH, and testosterone concentrations among cotton seed-fed rats is an indication that the damage done by the CSM also involves higher brain (hypothalamus) level.
Oxidative stress has been implicated in infertility. The extent of oxidative stress in a living system can be inferred from the concentration of antioxidants which is inversely proportional to its rate of usage. Result obtained from this study showed a significant decrease (p < 0.05) in plasma concentrations of catalase, SOD, and GPx, and GSH (45.00 ± 2.77, 2.02 ± 0.10, 21.53 ± 6.10, and 3.00 ± 0.41, respectively) in cotton seed-fed rats when compared to values obtained from control (69.71 ± 4.63, 2.99 ± 0.20, 26.76 ± 0.56 and 4.24 ± 0.22) and rats administered with aqueous Cissus populnea suspension (79.18 ± 2.81, 4.29 ± 0.11, 27.66 ± 1.67 and 5.36 ± 0.34, respectively) (Table 2). This indicates that the administered cotton seed increases systemic ROS generation which caused some degree of hypothalamic damage and affectation of the hypothalamo-pituitary–testicular axis. The administered aqueous Cissus populnea suspension however ameliorates the existing oxidative stress as indicated by improvements in the observed decrease in plasma catalase, SOD, GPx, and GSH concentrations to 52.18 ± 6.88, 2.63 ± 0.24, 22.20 ± 4.68, and 4.30 ± 0.22 respectively (Table 2). In this situation, the non-enzymatic (GSH) and enzymatic (catalase, SOD, and GPx) antioxidants act synergistically to scavenge the cotton seed-induced generated ROS and thus annul or minimize their damaging effects.
Seminal fluid analysis remains an important non-invasive investigative means of diagnosing male infertility. The generally acceptable parameters for assessing male fertility potentials include ejaculation volume ≥ 1.5 mL, sperm concentration ≥ 15 million spermatozoa/mL, and total sperm count ≥ 39 million spermatozoa per ejaculate [32,33,34]. Normal morphologic and vitality feature requires that at least 4% of spermatozoan are of normal form, 58% living, having 40% of total spermatozoan motile (progressive + nonprogressive) and 32% of this showing progressive movement [32,33,34]. Result from this study showed a significant reduction (p < 0.05) in the sperm parameters (Count 7.33 ± 2.15; motility 45.50 ± 5.73; morphology 3.25 ± 0.46; vitality 84.25 ± 4.05; and non-vitality 1.000 ± 0.000) among rats fed with cotton seed meal when compared to control rats (Count 21.00 ± 3.43, Motility 91.00 ± 2.93; morphology 3.75 ± 0.46; vitality 87.50 ± 2.67; and non-vitality 1.125 ± 0.230) and aqueous Cissus populnea suspension-fed rats (Count 36.83 ± 5.39, Motility 96.86 ± 1.35; morphology 3.74 ± 0.49; vitality 94.00 ± 3.83; and non-vitality 1.125 ± 0.232) (Table 3). Similar alterations in sperm characteristics had earlier been reported among Wistar rats fed with cotton seed by researchers [35, 36]. The observed low sperm count, morphologic alterations and reduction in sperm motility among rats fed with cotton seed meal are attributable to gossypol present in the administered CSM which has immobilizing effect on spermatozoa and generate large amounts of ROS that oxidatively damage the germinal epithelium and spermatozoan plasma membrane causing reduction in the spermatozoan qualities (counts, morphology, motility, viability), sperm dysfunction or even sperm death. Meanwhile, improvements in these parameters (Count 14.30 ± 1.50; motility 50.00 ± 23.91; morphology 4.00 ± 0.00; vitality 85.50 ± 7.03; and non-vitality 1.121 ± 0.233) were observed after the administration of aqueous Cissus populnea suspension. This is suggestive of spermatogenic effect of aqueous Cissus populnea suspension as against the earlier reported no effect on fertility . The observed spermatogenic effect of aqueous Cissus populnea suspension is ascribed to the presence of phytochemicals with antioxidative activities which mop-up the gossypol-induced generated ROS thereby annulling the damaging effects on the testes and sperm cells. However, in vitro studies using Sertoli cell lines have been reported to increase cell proliferation which plays critical roles in spermatogenesis [31, 37].
The photomicrograph of the testes showed normal seminiferous tubules, interstitial and Leydig cells appearances; and adluminal area packed with spermatozoa among the control rats (Fig. 1). On the other hand, abnormal interstitial appearances and absent Leydig cells were observed in many areas among cotton seed-fed rats (Fig. 1). Improvements in the histologic appearances were however observed to occur among rats administered with aqueous Cissus populnea suspension as evident by having few germinal cell loss, partial abnormal interstitial appearances, absent Leydig cells in few areas and adluminal areas sparingly packed with spermatozoa (Fig. 1). These findings agree with report from similar studies [31, 37] and confirm the observed improvements in serum hormones and other biochemical parameters by the administered aqueous Cissus populnea suspension. The observed testicular damage among rats fed with cotton seed reflects existing oxidative stress caused by the associated imbalance between systemic ROS generation and antioxidants activities. The observed improvements occur as a result of some phytochemicals present in the aqueous suspension which stimulate the hypothalamo-pituitary–testicular axis and regenerate the hypothalamus and germ cells in the testes.