Abstract
To determine the effects of zinc and the active vitamin D_3 on the mandible formation in vivo, thirty Wistar male rats, aged five weeks old, were divided into four groups randomly as follows. The control group was fed on the standard diet ; the standard diet group, low zinc experimental group, high zinc experimental group were fed on the standard, low-zinc and high-zinc diet respectively, and orally administered 1α-OH-D_3. After four weeks of feeding, the effects of zinc and active vitamin D_3 were investigated. The weight of the control group showed no significant difference from the other three groups, but the weight of the high zinc experimental group was significantly higher than that of the low zinc experiment group. The bone mineral mass of the high zinc experimental group was significantly higher than that of the low zinc experiment group. As compared with the control group on the histological observation, the low zinc experimental group showed thin bone layer, increasing of demineralized structures, and the bone lacunae surrounding Havers canaliculi irregular and loose. In the standard diet group, the Havers canaliculi, bone lacunae and thickness of bone showed increasing tendency. The high zinc experimental group showed some active characters including the active increasing in thickness of bone, density of Havers system, bone lacunae, active bone remodeling. In the low zinc experimental group, bone resorption areas covered by loose webs of collagen fibers were wide in comparison with bone formation areas on the scanning electron microscopic observation. In the high zinc experimental group, inactive bone matrix formation areas covered by collagen fibers were often observed. In the standard diet group and the control group, the similar views were found. In endocrine level examination of the hematological test, the calcitonin level of the low zinc experimental group was significantly lower than that of the control group. That suggested that inadequate zinc intake restrained bone resorption. The present study suggested that the active vitamin D_3 and zinc could take a positive action on bone metabolism. The active vitamin D_3 was helpful to bone remodeling, but increasing 1α-OH-D_3 alone hardly had any effect on bone debility caused by inadequate zinc intake.
