Previously, we reported that the administration of a mixture of Humulus japonicus (MH) increased the longitudinal bone growth rate in Sprague Dawley rats. In this study, we investigated the effects of the dietary administration of MH on longitudinal bone growth in growth hormone (GH)-deficient hypophysectomized male and female rats to determine whether the effect of MH was similar to that of GH. We measured the nose-to-anus and nose-to-tail length gain, femur and tibia lengths, growth plate zones, and expression of insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) after the dietary administration of MH or the injection of GH into hypophysectomized rats for 4 weeks. Results demonstrated that the dietary administration of MH had no effect on longitudinal bone growth, whereas the injection of GH increased the nose-to-tail length gain and femur and tibia lengths in hypophysectomized rats. In addition, MH did not affect the growth plate, bone mineralization, and expression of IGF-1 and IGFBP-3. These findings indicate that MH does not exert a GH-like effect and that the effects of MH and GH on longitudinal bone growth involve different pathways.
Keywords: Humulus japonicas; hypophysectomized rats; longitudinal bone growth.