IGF receptors in myocardial capillary endothelium: potential regulation of IGF-I transport to cardiac muscle
Bar, R.S.; Boes, M.; Sandra, A.
Biochemical and Biophysical Research Communications 152(1): 93-98
1988
ISSN/ISBN: 0006-291X PMID: 2965874 Document Number: 307111
Beating rat hearts were perfused with 125I-IGF-II alone or 125I-IGF-II and unlabeled IGF-II or insulin, then prepared for radioautography. Maximal 125I-IGF-II grain counts over capillaries were decreased in a dose-dependent manner by unlabeled IGF-II but were unaffected by coperfusion with insulin. To determine a potential role for capillary receptors in the transfer of circulating IGF to cardiac muscle, the effects of sequential loss of capillary IGF binding sites was determined. For IGF-I, loss of capillary binding sites by trypsin perfusion was accompanied by proportional decreases in the subsequent appearance of IGF-I in cardiac muscle. In contrast, similar decrements of capillary IGF-II binding did not affect muscle levels of IGF-II. We conclude that capillary endothelium of the intact heart possesses distinct IGF-I and IGF-II binding sites, with the capillary IGF-I binding sites being of potential importance in the transfer of vascular IGF-I to subendothelial cardiac muscle.