Glucose-regulated protein 78 (GRP78) is elevated in embryonic mouse heart and induced following hypoglycemic stress

This study investigates the distribution and heart levels of glucose regula ted protein (GRP) 78 during normal development and in response to hypoglyce mia in the mouse. Results demonstrate that GRP78 is strongly expressed with in the heart, neural tube, gut endoderm, somites, and surface ectoderm of mouse embryos during early organogenesis, and GRP78 staining remains promin ent in the heart from gestational days 9.5 through 13.5. Cardiac myocytes a re the primary site of GRP78 expression within the heart. GRP78 levels are highest in the heart during early organogenesis and levels decrease signifi cantly by the fetal period. GRP78 expression is increased after 24 h of hyp oglycemia in the early organogenesis-stage heart. Considering the tissue sp ecific pattern of GRP expression and changes during development of the hear t, GRPs may play significant roles in the normal differentiation and develo pment of cardiac tissue. GRP induction may also be involved in hypoglycemia -induced cardiac dysmorphogenesis.