IGF-I expression in blood vessels varies with vascular load

The present study was designed to investigate if the immunoreactivity of insulin-like growth factor I (IGF-I, somatomedin C) in blood vessels was changed in relation to the vascular load in adult rats. Occlusion of the right femoral artery resulted within 24 h in a strongly increased IGF-I immunoreactivity in the media of the contralateral, left, femoral artery and a significant decrease in the IGF-I expression in the right femoral artery distal to the occlusion. The increased labelling of the smooth muscle cells persisted for at least 21 days. Inactivity of the right hind limb, secondarily to an ischaemic insult, likewise induced a significant increase in IGF-I immunoreactivity, within 24 h, in the femoral vessels of the undamaged, contralateral left hind limb. It is concluded that IGF-I immunoreactivity varies with the dynamic load in the vascular walls. It is proposed that IGF-I may serve as a parahormone exerting its effect by paracrine and/or autocrine mechanisms, taking part in regulating the structural adaption of blood vessels in response to stress.