From the Departments of Internal Medicine and Obstetrics/Gynecology,
University of Iowa College of Medicine, and Department of Veterans Affairs
Medical Center, Iowa City, Iowa.
AbstractIn normotensive rats,
increased renal pelvic pressure stimulates the release of
prostaglandin E and substance P, which in turn leads to an
increase in afferent renal nerve activity (ARNA) and a contralateral
natriuresis, a contralateral inhibitory renorenal reflex.
In spontaneously hypertensive rats (SHR), increasing renal pelvic
pressure failed to increase afferent renal nerve activity. The
inhibitory nature of renorenal reflexes indicates that
impaired renorenal reflexes could contribute to increased sodium
retention in SHR. Phorbol esters, known to activate protein
kinase C, increase afferent renal nerve activity in Wistar-Kyoto rats
(WKY) but not in SHR. We examined the mechanisms involved in the
impaired responses to renal sensory receptor activation in SHR. The
phorbol ester 4ß-phorbol 12,13-dibutyrate increased renal pelvic
protein kinase C activity similarly in SHR and WKY. Increasing renal
pelvic pressure increased afferent renal nerve activity in WKY
(27±2%) but not in SHR. Renal pelvic release of
prostaglandin E increased similarly in WKY and SHR, from
0.8±0.1 to 2.0±0.4 ng/min and 0.7±0.1 to 1.4±0.2 ng/min. Renal
pelvic release of substance P was greater (P<.01) in
WKY, from 16.3±3.8 to 41.8±7.4 pg/min, than in SHR, from 9.9±1.7 to
17.0±3.2 pg/min. In WKY, renal pelvic administration of substance P at
0.8, 4, and 20 µg/mL increased ARNA 382±69, 750±233, and
783±124% · second (area under the curve of afferent renal
nerve activity versus time). In SHR, substance P at 0.8 to 20 µg/mL
failed to increase ARNA. These findings demonstrate that the impaired
afferent renal nerve activity response to increased renal pelvic
pressure is related to decreased release of substance P and/or impaired
activation of substance P receptors.
© 1998 American Heart Association, Inc.
Scientific Contributions
Renal Substance PContaining Neurons and Substance P Receptors Impaired in Hypertension
Key Words: afferent renal nerve activity receptors, sensory prostaglandins protein kinase C substance P rats, inbred SHR
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