Abstract:An increasing number of pathophysiological roles for purinoceptors are emerging, some of which have therapeutic potential. Erythrocytes are an important source of purines, which can be released under physiological and physiopathological conditions, acting on purinergic receptors associated with the same cell or with neighboring cells. Few studies have been conducted on lizards, and have been limited to ATP agonist itself. We have previously shown that the red blood cells (RBCs) of the lizard Ameiva ameiva stor… Show more
“…2001). A later study suggested that this was a P2Y 4 ‐like receptor as UTP was a potent agonist (Sartorello & Garcia 2005). Activation of this receptor resulted in InsP 3 production and Ca 2+ mobilization from the ER.…”
Purines appear to be the most primitive and widespread chemical messengers in the animal and plant kingdoms. The evidence for purinergic signalling in plants, invertebrates and lower vertebrates is reviewed. Much is based on pharmacological studies, but important recent studies have utilized the techniques of molecular biology and receptors have been cloned and characterized in primitive invertebrates, including the social amoeba Dictyostelium and the platyhelminth Schistosoma, as well as the green algae Ostreococcus, which resemble P2X receptors identified in mammals. This suggests that contrary to earlier speculations, P2X ion channel receptors appeared early in evolution, while G protein-coupled P1 and P2Y receptors were introduced either at the same time or perhaps even later. The absence of gene coding for P2X receptors in some animal groups [e.g. in some insects, roundworms (Caenorhabditis elegans) and the plant Arabidopsis] in contrast to the potent pharmacological actions of nucleotides in the same species, suggests that novel receptors are still to be discovered.
“…2001). A later study suggested that this was a P2Y 4 ‐like receptor as UTP was a potent agonist (Sartorello & Garcia 2005). Activation of this receptor resulted in InsP 3 production and Ca 2+ mobilization from the ER.…”
Purines appear to be the most primitive and widespread chemical messengers in the animal and plant kingdoms. The evidence for purinergic signalling in plants, invertebrates and lower vertebrates is reviewed. Much is based on pharmacological studies, but important recent studies have utilized the techniques of molecular biology and receptors have been cloned and characterized in primitive invertebrates, including the social amoeba Dictyostelium and the platyhelminth Schistosoma, as well as the green algae Ostreococcus, which resemble P2X receptors identified in mammals. This suggests that contrary to earlier speculations, P2X ion channel receptors appeared early in evolution, while G protein-coupled P1 and P2Y receptors were introduced either at the same time or perhaps even later. The absence of gene coding for P2X receptors in some animal groups [e.g. in some insects, roundworms (Caenorhabditis elegans) and the plant Arabidopsis] in contrast to the potent pharmacological actions of nucleotides in the same species, suggests that novel receptors are still to be discovered.
“…Present in the immature stage of mammalian erythrocytes, birds, amphibians, fishes and reptiles, nucleated RBCs differ from mature mammalian erythrocytes by the presence of a nucleus and organelles. Despite this, few studies of the mechanisms of Ca 2+ homeostasis in nucleated RBCs have been performed [ 15 , 16 ]. By studying signal transduction pathways in lizard RBCs from different families, we have been able to infer phylogenetic aspects and mechanisms for these cells to maintain its Ca 2+ homeostasis.…”
Background: We have previously reported that a Teiid lizard red blood cells (RBCs) such as Ameiva ameiva and Tupinambis merianae controls intracellular calcium levels by displaying multiple mechanisms. In these cells, calcium stores could be discharged not only by: thapsigargin, but also by the Na + /H + ionophore monensin, K + /H + ionophore nigericin and the H + pump inhibitor bafilomycin as well as ionomycin. Moreover, these lizards possess a P2Y-type purinoceptors that mobilize Ca 2+ from intracellular stores upon ATP addition.
“…This evidence shows that the increase in calcium concentration was not due to ionic influx, discarding the possibility for these cells to display P2X purinoceptors (Beraldo et al, 2001). In A. ameiva RBCs, a pharmacological characterization of the purinoceptor, evidenced a P2Y 4 -like receptor, since UTP, UDP, GTP, ATPγS evoked a dose-dependent calcium response, and 2MeSATP, 2ClATP, α,β-ATP and ADP failed to promote a elevation in [Ca 2+ ] i (Sartorello and Garcia, 2005).…”
The ion calcium is a ubiquitous second messenger, present in all eukaryotic cells. It modulates a vast number of cellular events, such as cell division and differentiation, fertilization, cell volume, decodification of external stimuli. To process this variety of information, the cells display a number of calcium pools, which are capable of mobilization for signaling purposes. Here we review the calcium signaling on lizards red blood cells, an interesting model that has been receiving an increasing notice recently. These cells possess a complex machinery to regulate calcium, and display calcium responses to extracellular agonists. Interestingly, the pattern of calcium handling and response are divergent in different lizard families, which enforces the morphological data to their phylogenetic classification, and suggest the radiation of different calcium signaling models in lizards evolution.
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