Activation of a P2Y4-like purinoceptor triggers an increase in cytosolic [Ca2+] in the red blood cells of the lizard Ameiva ameiva (Squamata, Teiidae)

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 store Ca 2+ in the endoplasmic reticulum (ER) and that the purinergic agonist ATP triggers a rapid and transient increase of [Ca 2+ ] c by mobilization of the cation from internal stores. We also reported the ability of the second messenger IP 3 to discharge the ER calcium pool of the ER. Here we characterize the purinoceptor present in the cytoplasmic membrane of the RBCs of the lizard Ameiva ameiva by the selective use of ATP analogues and pyrimidine nucleotides. The nucleotides UTP, UDP, GTP, and ATPγS triggered a dose-dependent response, while interestingly 2MeSATP, 2ClATP, α,ß-ATP, and ADP failed to do so in a 1-to 200-µm concentration. The EC 50 obtained for the compounds tested was 41.77 µM for UTP, 48.11 µM for GTP, 53.11 µM for UDP, and 30.78 µM for ATPγS. The present data indicate that the receptor within the RBCs of Ameiva ameiva is a P2Y 4 -like receptor due to its pharmacological similarity to the mammalian P2Y 4 receptor.

Evolutionary origins of the purinergic signalling system

“…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.…”

Divergent calcium signaling in RBCs from Tropidurus torquatus (Squamata – Tropiduridae) strengthen classification in lizard evolution

“…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.…”

Inter-relação do ritmo e da ação de drogas antimaláricas na infecção da malária de roedores

“…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).…”