Decreases in Substance P and Vasoactive Intestinal Peptide Concentrations in Plasma of Stroke-Prone Spontaneously Hypertensive Rats.

In order to study alterations of peripheral substance P (SP) and vasoactive intestinal peptide (VIP) in the immunoreactive nervous system in essential hypertension, plasma SP and VIP concentrations in stroke-prone spontaneously hypertensive rats (SHRSP) at 8, 12, 18, 28, 30, 35 and 48 weeks of age and agematched Wistar-Kyoto rats (WKY) were measured, using enzyme immunoassays (EIAs).The mean plasma SP concentrations of SHRSP (n=61) and WKY (n=58) were 4.9±1.2fmol/ml and 6.6±1.9fmol/ml, respectively. The value of SHRSP was significantly lower than that of WKY (p<0.01). The mean SP concentration of young SHRSP was significantly higher than those of other ages.The mean plasma VIP concentrations of SHRSP (n=61) and WKY (n=58) were 0.80±0.25fmol/ml and 1.01±0.32fmol/ml, respectively. The value of SHRSP was significantly lower than that of WKY (p<0.01).These decreases in plasma SP and VIP concentrations of SHRSP were observed at all ages. Decreases in the peripheral release of SP and VIP from the endings of SP- and VIP-immunoreactive nerves of SHRSP were seen, and the functional involution of peripheral SP- and VIP-immunoreactive nerves in essential hypertension was suggested.