AJP - Regulatory, Integrative and Comparative Physiology, Vol 263, Issue 2 405-R411, Copyright © 1992 by American Physiological Society
beta-Adrenoceptor modulation of renin response to short-term reductions in pressure in young SHR
J. P. Porter
Department of Physiology, University of Louisville, Kentucky 40292.
The increase in renin secretion in response to short-term (5 min)
reductions in arterial pressure has recently been shown to be similar in
young spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto
(WKY) animals. This was puzzling, since tonic renal nerve activity is
thought to be elevated in the young SHR, and this has the potential to
enhance the renin response. The purpose of the present investigation was to
determine whether beta-adrenoceptor modulation of pressure-dependent renin
release is diminished in the SHR. In conscious, age-matched SHR, WKY, and
Sprague-Dawley rats, the effect on arterial plasma renin activity of 5-min
reductions in renal perfusion pressure to 90 and 50 mmHg was determined
before and during beta-adrenoceptor activation with isoproterenol or
beta-adrenoceptor blockade with propranolol. Isoproterenol augmented the
renin response at 50 mmHg in all three strains, with the greatest effect
occurring in the Sprague-Dawley rats. The response at 90 mmHg was also
enhanced in the SHR and Sprague-Dawley rats, but not the WKY rats.
Propranolol had no effect in the SHR and WKY animals, but significantly
reduced the renin response at 50 mmHg in the Sprague-Dawley rats. Thus,
under the conditions of the present investigation (i.e., short-term
reductions in pressure), tonic renal nerve activity does not affect
pressure-dependent renin release through a beta-adrenergic receptor
mechanism in either the SHR or WKY rats. However, under conditions of acute
beta-adrenoceptor activation, the renin response is enhanced at a higher
renal perfusion pressure in the SHR than in the WKY rat.
