Changes in purinergic signalling in developing and ageing rat tail artery: Importance for temperature control
Introduction
It is now recognised that extracellular purines (adenosine, adenosine diphosphate (ADP) and adenosine 5′-triphosphate (ATP)) and pyrimidines (uridine diphosphate (UDP) and uridine 5′-triphosphate (UTP)) are important extracellular signalling molecules that mediate diverse effects on many biological processes (see Ralevic and Burnstock, 1998, Burnstock and Knight, 2004). Currently, seven mammalian P2X ionotropic ligand-gated ion channel receptors (P2X1–7) and eight P2Y metabotropic G protein-coupled receptors (P2Y1, P2Y2, P2Y4, P2Y6, P2Y11, P2Y12, P2Y13 and P2Y14) have been identified (Burnstock, 2004).
There is much evidence showing the existence of sympathetic purinergic co-transmission involving noradrenaline (NA) and ATP in a variety of blood vessels, including the tail artery of the rat (Sneddon and Burnstock, 1985) and the mesenteric artery of the guinea pig and rat (Ishikawa, 1985, Sjöblom-Widfeldt, 1990). The sympathetic nerves supplying different blood vessels release a variable ratio of NA:ATP, the purinergic component being relatively minor (∼10%) in the rat tail artery (Bao et al., 1993), whereas in the rabbit splenic artery, nerve-mediated responses are largely purinergic (Ren and Burnstock, 1997). In the rabbit mesenteric artery ATP is the sole excitatory transmitter, although NA is released and contributes to feedback inhibition (Ramme et al., 1987).
P2 receptors are widely distributed in the cardiovascular system and are important in the regulation of vascular tone (Boarder and Hourani, 1998). The P2X1 receptor is the principal P2X receptor subtype expressed on most vascular smooth muscles (Valera et al., 1994, Collo et al., 1996) and Bo and Burnstock (1993) reported that the smooth muscle of the rat tail artery has a high density of P2X1 receptors.
P2X2 receptor immunoreactivity has been visualised on smooth muscle cells of rat mesenteric, renal and pulmonary arteries, although at a lower density than P2X1 (Hansen et al., 1999). In addition, P2X4 receptors have also been visualised in rat aorta and vena cava as well as coronary, pulmonary, renal and femoral arteries (Soto et al., 1996, Nori et al., 1998).
Metabotropic P2Y receptors also participate in the control of vascular tone. At least four P2Y receptor subtypes mediate the vascular effects of extracellular nucleotides, namely P2Y1, P2Y2, P2Y4 and P2Y6 receptors. P2Y1 receptors are activated by the endogenous ligands ADP and ATP; in contrast P2Y2, P2Y4 and P2Y6 receptors are activated by uridine nucleotides. UTP was found to be equipotent with ATP at evoking contraction of the tail artery (Evans and Kennedy, 1994), suggestive of two populations of P2 receptors (McLaren et al., 1998), the second population being G protein-coupled P2Y2 and P2Y4 receptors.
P2Y1 receptors are distributed on both vascular smooth muscle and endothelium. When present on the endothelium they mediate vasodilatation via endothelial nitric oxide (NO; Moncada et al., 1991) and also by the generation of endothelium-dependent hyperpolarising factor (EDHF: Malmsjö et al., 1999, Stanford et al., 2001). Smooth muscle P2Y1 receptors also produce vasodilatation of a number of blood vessels, including the rabbit mesenteric artery (Mathieson and Burnstock, 1985, Burnstock and Warland, 1987) and vasoconstriction of others (Knight et al., 2003, Steinmetz et al., 2003). Similarly P2Y2 receptors in the vasculature are either present on the endothelium, such as in the rat and golden hamster isolated mesenteric arterial beds (Ralevic and Burnstock, 1996a, Ralevic and Burnstock, 1996b), where they mediate vasodilatation via NO synthesis and release, or on smooth muscle as in the rat and bovine middle cerebral artery (Miyagi et al., 1996) where they mediate contraction. In the rat tail and femoral arteries, UTP has been shown to produce vasoconstriction (Saïag et al., 1990).
Ageing produces changes in vascular smooth muscle cells and endothelial cells (Wei, 1992). These changes include thickening of the media and enlargement of the lumen diameter, increased stiffening and an accompanying reduction in arterial distensibility of larger vessels (see Moreau et al., 1998, Laurant et al., 2004). Generally, there is a reduced tendency for endothelium-dependent relaxation and endothelial release of NO with increasing age (Hynes and Duckles, 1987). Relaxations to histamine decline during ageing in the rat mesenteric artery (Moritoki et al., 1986), as do relaxations to ACh, partly due to reduced hyperpolarisation by EDHF (Marín, 1995). Endothelial-dependent relaxations to ATP and acetylcholine (ACh) are impaired in carotid arteries from old and hypertensive rats (Hongo et al., 1988). Endothelium-independent vasodilatations are also modified with age (Docherty, 1990, Marín, 1995).
There is a reduction during ageing in the maximum contractile responses induced by NA in rat, rabbit and guinea-pig aortae, dog and monkey mesenteric arteries, dog cerebral arteries and rat tail arteries (Fouda and Atkinson, 1986, Marín, 1995). In contrast, contractions to NA are increased with age in isolated dog iliac, carotid, renal and mesenteric arteries (Cox et al., 1976), ear artery from lambs and ewes (Wyse et al., 1977) and rat aorta (Olah and Rahwan, 1987). The isolated rabbit aorta (Hayashi and Toda, 1978) and rat femoral and carotid arteries (Duckles et al., 1985) are unaffected by increasing age.
Considerable plasticity during development and ageing of the autonomic nervous system in terms of co-transmitter expression and function is apparent. Hormones, disease, surgery and trauma can also underlie plasticity in the autonomic nervous system (Burnstock, 1997). Changes in the structure of neurons and nerves (Cowen, 1993) and on adrenergic neurotransmission in the sympathetic nervous system occur with age. Neuron structure can change, as well as a reduction in neuron number and loss of nerve fibres. Dhall et al. (1986) showed developmental changes in perivascular noradrenergic and peptide-containing nerves in the guinea pig; noradrenergic nerve density peaked 4 weeks after birth whilst nerves containing VIP, CGRP and SP peaked at birth and declined thereafter in the mesenteric and carotid arteries.
The rat tail artery is important for both balance and thermoregulation. Body appendages, such as the tail, are important heat exchange sites where increases in blood flow cause heat dissipation. Skin blood flow results in heat loss from the surface and this is modified by a sympathetically mediated mechanism. The tail of the rat functions as a heat-loss organ since it lacks hair covering, has a large surface area to volume ratio and is highly vascularised with arteriovenous anastomoses (Gordon, 1990). Up to 20% of total body heat loss can occur via the tail.
The aim of this study was to examine the expression and function of P2 receptors in the rat tail and mesenteric arteries during maturation and ageing. Rats attain sexual maturity at 2–3 months of age; they show rapid growth up to 8–9 months, which becomes stable by about 12 months. Twenty-four months is a commonly accepted age for senescence in rats (Weihe, 1987). For this study young rats of 4 and 6 weeks old were used to show any changes occurring in the early life of a rat, 12-week-old rats were used to reflect any changes as sexual maturity was reached, 8-month-old adult rats whose rapid growth was beginning to slow down and old (senescent) rats aged 24 months were used.
Section snippets
General procedures
Male Sprague–Dawley rats, aged 4, 6 and 12 weeks, 8 and 24 months, were killed according to Home Office (UK) regulations covering Schedule one procedures–by asphyxiation with CO2 and subsequent cervical dislocation to confirm death. The tail and mesenteric arteries were dissected free, carefully cleaned of adhering fat and excessive connective tissue. The arteries were cut into rings approximately 4 mm in length and mounted horizontally for tension recording by inserting two tungsten wires through
Responses to nerve stimulation in the tail artery
EFS of the tail arteries from each age group induced sympathetic nerve-mediated, frequency-dependent contractions that were TTX (1 μM) sensitive. In the presence of suramin (100 μM) alone (Fig. 1a–e), contractile responses induced by EFS in all age groups were significantly inhibited (P < 0.05 or less). When the frequency–response curves were repeated in the presence of suramin and prazosin (1 μM) contractions were almost completely inhibited for each age group (P < 0.001). Conversely, when the curves
Discussion
This study has shown that the function and expression of P2X and P2Y receptors of the rat tail and mesenteric artery alter with maturation and age. In general the trend is for the sensitivity and expression of P2X and P2Y receptors to decrease as the age of the animal increases. However, there were significant differences between the two vessels examined that include transient maturational increases in the expression of selected receptors in the mesenteric artery.
Bao et al. (1993) previously
Acknowledgements
The authors thank Dr H.-Z. Ruan for invaluable assistance with immunohistochemistry, and Mr Tim Robson for excellent technical assistance.
References (72)
- et al.
The regulation of vascular function by P2 receptors: multiple sites and multiple receptors
Trends Pharmacol. Sci.
(1998) The past, present and future of purine nucleotides as signalling molecules
Neuropharmacology
(1997)- et al.
Cellular distribution and functions of P2 receptor subtypes in different systems
Int. Rev. Cytol.
(2004) Ageing in the autonomic nervous system: a result of nerve-target interactions? A review
Mech. Ageing Dev.
(1993)- et al.
Perivascular noradrenergic and peptide-containing nerves show different patterns of change during development and ageing in the guinea-pig
J. Auton. Nerv. Syst.
(1986) Extracellular ATP: a growth factor for vascular smooth muscle cells
Gen. Pharmacol.
(1998)Thermal biology of the laboratory rat
Physiol. Behav.
(1990)- et al.
P2X (purinergic) receptor distributions in rat blood vessels
J. Auton. Nerv. Syst.
(1999) - et al.
Unusual absence of endothelium-dependent or -independent vasodilatation to purines or pyrimidines in the rat renal artery
Kidney Int.
(2003) - et al.
Age-related changes in adenosine 5′-triphosphate-induced constriction of isolated, perfused mesenteric arteries of rats
Life Sci.
(1999)
The tungstate-stabilized tetramethylbenzidine reaction for light and electron microscopic immunocytochemistry and for revealing biocytin filled neurons
J. Neurosci. Methods
Endothelial P2Y receptors induce hyperpolarisation of vascular smooth muscle by release of endothelium-derived hyperpolarising factor
Eur. J. Pharmacol.
Age-related changes in vascular responses: a review
Mech. Ageing Dev.
Purine-mediated relaxation and constriction of rabbit isolated mesenteric artery are not endothelium-dependent
Eur. J. Pharmacol.
Age-related changes in P2 receptor mRNA of rat cerebral arteries
Exp. Gerontol.
Age-related decrease in endothelium-dependent dilator response to histamine in rat mesenteric artery
Eur. J. Pharmacol.
Influence of age on calcium entry blocking drugs in rat aorta is spasmogen-dependent
Eur. J. Pharmacol.
Age-related variations in the relative importance of noradrenaline and ATP as mediators of the contractile response of rat tail artery to sympathetic nerve stimulation
Acta Physiol. Scand.
Frequency- and train length-dependent variation in the roles of postjunctional alpha 1- and alpha 2-adrenoceptors for the filed stimulation-induced neurogenic contraction of rat tail artery
Naunyn-Schmiedeberg's Arch. Pharmacol.
Heterogeneous distribution of [3H] α, β-methylene ATP binding sites in blood vessels
J. Vasc. Res.
Responses of rabbit basilar arteries to vasoconstrictor and vasodilator agents: the effects of atherosclerosis, age and sex
J. Vasc. Res.
Purinergic signalling and vascular cell proliferation and death
Arterioscler. Thromb. Vasc. Biol.
Introduction: P2 receptors
Curr. Top. Med. Chem.
P2-Purinoceptors of two subtypes in the rabbit mesenteric artery: Reactive blue selectively inhibits responses mediated via the P2Y- but not P2X-purinoceptor
Br. J. Pharmacol.
Cloning of P2X5 and P2X6 receptors and the distribution and properties of an extended family of ATP-gated ion channels
J. Neurosci.
Mechanics and electrolyte composition of arterial smooth muscle in developing dogs
Am. J. Physiol.
Cardiovascular responses in ageing: a review
Pharmacol. Rev.
Vascular adrenergic neuroeffector function does not decline in aged rats
Circ. Res.
Characterisation of P2-purinoceptors in the smooth muscle of the rat tail artery; a comparison between contractile and electrophysiological responses
Br. J. Pharmacol.
Sensitivity to noradrenaline and electrical stimulation decreases with age in the rat tail artery
Naunyn-Schmiedeberg's Arch. Pharmacol.
Properties of P2X and P2Y receptors are dependent on artery diameter in the rat mesenteric bed
Br. J. Pharmacol.
P2X4 and P2X6 receptors associate with VE-cadherin in human endothelial cells
Cell. Mol. Life Sci.
Age-related changes in the response of rabbit isolated aortae to vasoactive agents
Br. J. Pharmacol.
Effects of aging and hypertension on endothelium-dependent vascular relaxation in rat carotid artery
Stroke
Effect of increasing age on the endothelium-mediated relaxation of rat blood vessels in vitro
J. Pharmacol. Exp. Ther.
Actions of ATP and α, β-methylene ATP on neurotransmission and smooth muscle membrane of the rabbit and guinea-pig mesenteric arteries
Br. J. Pharmacol.
Cited by (22)
Purinergic signalling and development of the autonomic nervous system
2015, Autonomic Neuroscience: Basic and ClinicalCitation Excerpt :A reduction in spontaneous and α-adrenoceptor-induced release of ATP from endothelial cells of the rat tail artery occurs with advancing age (Hashimoto et al., 1995). The shift from purinergic to adrenergic signaling was confirmed and also showed that the responses to ATP and α,β-meATP, as well as the expression of P2X receptors, decreased with age (Wallace et al., 2006). Contractile responses to 2-methylthio ADP and UTP and expression of P2Y1 and P2Y2 receptors, respectively, decreased also with age.
Extracellular ATP signaling in equine digital blood vessels
2013, European Journal of PharmacologyCitation Excerpt :It is generally accepted that P2X receptors play a role in the maintenance of vascular tone, and depending on their location and expression, can mediate both vasoconstriction (e.g. P2X1), and/or vasodilation (e.g. P2X2 and/or P2X4) (Burnstock, 2010). P2Y receptors are involved in mediating vasodilatation (Wallace et al., 2006). P2Y1, 2, 4, 6 receptors have been shown to mediate endothelium-dependent vasodilatation (Knight et al., 2003).
Dual effects of ATP on isolated arteries of the bovine eye
2012, Pharmacological ResearchCitation Excerpt :Since P2X3 subtype is mainly present in nerve cells [25], we propose that in the studied arteries α,β-meATP most likely interacts with the P2X1 subtype. The presence of these receptors was also shown in other arteries: intrarenal arteries [26], middle cerebral arteries [27], rat tail artery [28], coronary arteries and aorta [29], human umbilical arteries [30] and mesenteric artery [31]. For relaxative responses of the arteries, the strongest agents for PCA were adenosine and ATP, while for OA it was carbachol.
Age-related changes in P2Y receptor signalling in mouse cochlear supporting cells
2023, Journal of PhysiologyComparison of mRNA Expression of P2X Receptor Subtypes in Different Arterial Tissues of Rats
2020, Biochemical Genetics