Elevated concentrations of nerve growth factor in heart and mesenteric arteries of spontaneously hypertensive rats

Considerable evidence indicates an enhanced sympathetic innervation of muscular resistance arteries in the spontaneously hypertensive rat (SHR) compared with its normotensive Wistar-Kyoto (WKY) control. Since nerve growth factor (NGF) is known to affect the growth of sympathetic nerves, we have utilized a sensitive two-site enzyme linked immunoassay for NGF to compare to NGF content of hearts and mesenteric arteries of developing SHR and WKY rats. NGF levels in hearts revealed similar, although not identical, patterns of expression. In both strains, NGF levels declined from postnatal day 15, the earliest age examined, to stabilize at adult levels by postnatal day 32. Adult SHR concentrations were similar to those in age matched WKY controls. In contrast, in the mesenteric vascular bed, NGF levels of SHR were greater than those of WKY controls at all ages above 15 days. Moreover, these changes in NGF occurred concomitantly with increases in vascular mass are medial smooth muscle hyperplasia in the SHR. Whether abnormal NGF levels are a cause or consequence of vascular smooth muscle growth has yet to be determined. These results are consistant with the hypothesis that the hypernoradrenergic innervation of SHR vascular tissues results from an early elevation of NGF gene expression.