Effect of norepinephrine and acetylcholine on outer medullary
descending vasa recta.
Yang, Sai, Erik P. Silldorff, and Thomas L. Pallone, Division Of
Nephrology, The M. S. Hershey Medical Center, Pennsylvania State
University, Hershey, Pa 17033.
Thomas L. Pallone, M. D., Division of Nephrology, The Milton S.
Hershey Medical Center, P.O. Box 850, Hershey, PA 17033, (717)531
-8156 (Office), (717)531-6776 (FAX), tpallone@med.hmc.psu.edu
(Email)
APStracts 2:0118H, 1995.
In order to examine their reponsiveness to norepinephrine (NE) and
Acetylcholine (Ach), outer medullary descending vasa recta (OMDVR)
have been dissected from vascular bundles of the rat and perfused in
vitro. Abluminal application of NE produced graded vasoconstriction
in a concentration range of 10-9 to 10-6M. When applied with NE, Ach
at concentrations of 10-8 to 10-5M dilated NE preconstricted OMDVR.
In contrast, Ach applied in the absence of NE caused
vasoconstriction. Ach induced vasodilation was blocked by addition of
the nitric oxide synthase inhibitor N-w-nitro-arginine (LNNA, 2x10
-4M). LNNA in the absence of Ach enhanced NE induced vasoconstriction.
Supraphysiological (10-3M) L-arginine (L-Arg) reversed the effects of
LNNA and ablumenal application of LNNA alone resulted in OMDVR
vasoconstriction. At concentrations of 10-6 to 10-3M, ablumenal
application of L-Arg produced graded vasodilation of NE constricted
OMDVR. These results suggest that adrenergic and cholinergic
innervation could influence OMDVR vasomotor tone to modulate total
and regional blood flow to the renal medulla. The data also favor a
role for the activity of constitutively expressed nitric oxide
synthase to modulate OMDVR vasoactivity.
Received 28 November 1994; accepted in final form 15 March 1995.
APS Manuscript Number H1043-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 4 April 1995.