High doses of cobalt inhibited hair follicle development in Rex Rabbits

Abstract

<p>An experiment was conducted to investigate the effect of cobalt supplementation on hair follicle development in rabbits. Rex rabbits (30-d-old, n=180) were divided randomly into five equal treatment groups: rabbits fed a basal diet (control, measured cobalt content of 0.27 mg/kg) or rabbits fed a basal diet with an additional 0.1, 0.4, 1.6 or 6.4 mg/kg cobalt (in the form of cobalt sulfate) supplementation (measured cobalt contents of 0.35, 0.60, 1.83 and 6.62 mg/kg, respectively). Treatment with 6.4 mg/kg cobalt significantly decreased hair follicle density (<em>P</em><0.05), while low levels of cobalt (0.1-1.6 mg/kg) had no effect on hair follicle density (<em>P</em>>0.05). The addition of dietary cobalt at the highest level examined (6.4 mg/kg) significantly increased the gene expression of bone morphogenetic protein (BMP) 2 and BMP4 in skin tissue (<em>P</em><0.05), while the mRNA levels of versican, alkaline phosphatase, hepatocyte growth factor, and noggin remained unchanged (<em>P</em>>0.05). Compared with their levels in the control group, dietary cobalt treatment significantly suppressed the protein levels of p-mechanistic target of rapamycin (mTOR) and p-ribosomal protein S6 protein kinase (<em>P</em><0.05) but did not alter the protein levels of p-AMP-activated protein kinase, Wnt10b or p-β-catenin (<em>P</em>>0.05). In conclusion, cobalt at the highest concentration examined inhibited hair follicle development, which may have involved the mTOR-BMP signalling pathway.</p>