endings in the close vicinity to rat renal proximal tubules, increases the activity of Na+-K+-ATPase (NKA) in proximal convoluted tubules in a time-, temperature- and dosedependent manner. The effect is mimicked by the Y, receptor agonist, NPY,,_,,, but not by the Y, receptor agonist, [Leu3’, Pro3“] NPY. We have also examined the signaling pathways coupled to NPY. 1) the pretreatment of pertussis toxin blocks the stimulatory effect of NPY. 2) in rat proximal tubular cells in primary culture, NPY increases [CA2+li. 3) NPY stimulation of NKA activity is abolished in the presence of the specific calcium- and calmodulin-dependent protein phosphatase 2B inhibitor, FK 506. The NPY effect is attenuated by a-adrenoceptor antagonists prazosin and yohimbine. NPY 5 x 1O-9 M and oxymetazoline lo-* M alone have no effect on NKA activity but will together cause 63.2% increase of NKA activity from control. These results suggest an important role for this peptide in the regulation of the sodium balance in the kidney.
PYY binding by these analogues correlated with their activity in enhancing the vasoconstrictor response of phenylephrine. In addition, the displacement analysis revealed the presence of two binding sites for [des-Se?, Lys4]D-CysZ-NPY. NPY, PYY and the truncated and stabilized NPY fragments inhibit the electrically-evoked twitch responses in the vas deferens in a concentration-dependent manner. However, there was a gradual lowering ofthe potency with progressive shortening of the central amphipatic a-helical region. Moreover, the specific Y,-receptor agonist [Leu)‘, Pro34]NPY was poorly active; it suppressed the twitches by only 30% at the highest concentration (3 uM) investigated. In conclusion, these data indicate that the pre- and postjunctional effects ofNPY are mediated by Y,- and Y ,receptors respectively. The effects of [des-Se?, Lys4]DCy+NPY indicate that this NPY analogue might interact with a different site on the Y, receptor from that recognized by NPY in the rat tail artery.
C4/4 Effects of Various Neuropeptide Y Analogues on the Rat Tail Artery and Vas Deferens
C4l5 Neuropeptide Y Attenuates Parasympathetic Nerve-evoked Nasal Vasodilatation via Prejunctional Y, Receptors
M. Tschiipl*, R. C. Miller?, J. Pelton?, J.-C. Stoclet* and B. Bucher* *Laboratoire de Pharmacologic Cellulaire et Moleculaire, C.N.R.S. URA 600, ULP Strasbourg, B.P. 24,674Ol Illkirch, France and TMarion Merrell Dow Research Institut, 16, rue d’Ankara, B.P. 067,67046 Strasbourg, Cedex, France
J. S. Lacroix*, L. G. Ulman? and E. K. Potter? *University Hospital CH- 12 11 Geneva, Switzerland and tPrince of Wales Medical Research Institute, Randwick, 203 1 Sydney, NSW, Australia
The nasal mucosa is densely innervated by efferent sympathetic and parasympathetic nerves involved in the regulation of local blood flow and mucus secretion. In The effects of peptide Y (PYY) and various neuropeptide pentobarbitone anaesthetized dogs, preganglionic stimuY (NPY) related peptides on the perfused rat tail artery lation of the superior cervical sympathetic nerve (15 V, 1 ms) induced marked reduction of nasal arterial blood precontracted by phenylephrine and on the electricallyevoked twitches in the rat isolated vas deferens were comflow whereas stimulation of the parasympathetic nerve pared with the effects of NPY. (5 V, 1 ms) evoked frequency-dependent vasodilatation. NPY, PYY, [Le#, Pro34]NPY, [Glu16, Ser’*, Alazz, Sympathetic nerve stimulation ( 10 Hz, 3 min) evokedproLeu28*31]NPYand the centrally truncated and stabilized longed attenuation (p < 0.05) of the vasodilatory response analogues [D-Cy9, S-aminooctanoic acid”*“, Cy?‘]-NPY to subsequent parasympathetic stimulation. After preacid”“, CysZo]-NPY treatment with phentolamine, propranolol and ah-opine, and [D-Cys’, 8aminooctanoic 75 + 5% of the vasoconstrictor effect of sympathetic stimenhanced vasoconstriction evoked by previous exposure ulation remained but the parasympathetic nerve-evoked of the rat tail artery to 1 @I phenylephrine in a concenvasodilatation was not significantly modified, while the tration-dependent manner. NPY 13-36 and [des-Se?, Lys4, Cys*, S-aminooctanoic acid3-24,D-Cys*‘]-NPY were effects of exogenous noradrenaline and acetylcholine practically inactive, whereas [des-Se+, Lys4, D-Cys2, 8- were virtually abolished. Atropine-resistant parasympathetic vasodilation remained significantly attenuated for aminooctanoic acid3-24, Cysz7]-NPY ([des-Se?, Lys4]DCys*-NPY), was a weak agonist. There was a tendency for more than 30 min after the non-adrenergic sympathetic nerve-evoked vasoconstriction. Attenuation of parasymthe centrally truncated peptides to have progressively pathetic nerve-evoked vasodilatation could be mimicked lower EC,, values as the magnitude of the central aminoby exogenous NPY (50 nmol) and Y, receptor agonist Nacid deletion increased. When 1 @4 [des-Se?, Lys4]DCy+NPY was co-administered with either NPY or [[email protected]
, acetyl [LeuZ8,Leu-“] NPY 24-36 (50 nmol) but not by Y, Pro34]NPY the effects were additive, demonstrating that receptor agonist [Leu3’, Pro34] NPY. We conclude that sympathetic stimulation induces NPY release which attenit is not a partial agonist. Binding studies on membranes uates subsequent parasympathetic vasodilatation via prefrom SK-N-MC cells expressing Y,-receptors show that the rank order of potencies for displacement of the 12jI- junctional Yz receptors.