Impaired sperm characteristics in postpubertal growth-hormone-deficient dwarf (dw/dw) rats

The objective of the current study was to determine if sperm function is compromised in rats deficient in growth hormone (dw/dw) since a deficiency in this hormone has been implicated as a cause of lowered fertility and spermatogenic cessation in some biological models. Spermatozoa were recovered from the cauda epididymides of adult dwarf and Wistar control male rats. Spermatozoa were diluted in Medium 199 and analysed for motility. Aliquots were then fixed in phosphate buffered formalin, sperm concentration determined and morphology assessed. The mean measurements for percent motile and normal morphology were compared by Student's t-test. Sperm concentrations were compared by Mann-Whitney two sample test. The mean percentage of motile spermatozoa was significantly greater in the Wistar control group than in the dwarf group (75 +/- 1.44 vs 28 +/- 3.71%, P < 0.001). The percentage of normal sperm morphology was also greater in the Wistar control group (88 +/- 1.00 vs 75 +/- 6.9%, P < 0.001). The concentration of spermatozoa in the cauda epididymis was also significantly higher in the Wistar group. These results indicate that sperm function parameters are diminished in growth-hormone-deficient dw/dw rats. The effects of growth hormone deficiency in rats appears to be associated with compromised spermatogenesis as well as impaired sperm motility. The GH-deficient rat appears to be a suitable model for the study of the effects of GH on sperm characteristics.