The immunohistochemical investigation of the vascular endothelial growth factor (VEGF) in the lower vertebrate adenohypophysis and brain

We examined the distribution of the vascular endothelial growth factor (VEGF) in the adenohypophysis and brain of the reptiles, amphibians and teleosts by using immunohistochemical techniques. Antibodies generated against the human VEGF165 and against several adenohypophyseal hormones were used as immunohistochemical probes. In reptile, there is no immunopositive material against this VEGF antibody. In amphibians, no immunopositive material against this antibody was observed in the pituitary of Japanese newt and black-spotted pond frog. However, in Japanese tree frog, many VEGF immunopositive neurons were widely distributed in the brain. In several species of teleosts, the immunoreactive (ir)-VEGF cells corresponded with several thyroid stimulating hormone (TSH) producing cells which located in the pars distalis of the pituitary or somatolactin (SL) producing cells which existed in the pars intermedia of the pituitary. These results suggest that TSH and SL producing cells have a specific role other than endocrine function in each part of the adenohypophysis. The VEGF in the TSH and SL cells may be involved in the maintenance and control of the vascular permeability through a paracrine action within the adenohypophyseal capillary system.