Abstract
cADPR, a potent calcium-mobilizing intracellular messenger synthesized by ADP-ribosyl cyclases regulates openings of ryanodine receptors (RyR). Here we report that in the rat testis, a functional cADPR Ca2+ release system is essential for the contractile response of peritubular smooth muscle cells (PSMC) to endothelin (ET). We previously showed that this potent smooth muscle agonist elicits intracellular Ca2+ release in PSMC and seminiferous tubule contraction via activation of ETA and ETB receptors. ETB-R induces the mobilization of a thapsigargin-sensitive but IP3-independent intracellular Ca2+ pool. Stimulation of permeabilized PSMC with cADPR was found to elicit large Ca2+ releases blocked by either a selective antagonist of cADPR or a RyR blocker, but not by heparin. Western blotting and confocal fluorescence microscopy indicated the specific expression of type 2 RyR in perinuclear localization. ET was found to stimulate the activity of ADP-ribosyl cyclase. Microinjection of the selective cADPR antagonist 8NH2-cADPR completely abolished subsequent stimulation of Ca2+ signaling via ETA and ETB receptors. cADPR therefore appears to have an obligatory role for ETA-R and ETB-R-mediated calcium signaling in PSMC. However, ETB-R seem to be coupled exclusively to cADPR whereas ETA-R activation may be linked to IP3 and cADPR signaling pathways.
MeSH terms
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ADP-ribosyl Cyclase
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ADP-ribosyl Cyclase 1
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Adenosine Diphosphate Ribose / analogs & derivatives*
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Adenosine Diphosphate Ribose / antagonists & inhibitors
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Adenosine Diphosphate Ribose / pharmacology*
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Adenosine Diphosphate Ribose / physiology
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Animals
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Antigens, CD*
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Antigens, Differentiation / metabolism
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Blotting, Western
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Boron Compounds / chemistry
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Calcium Channels / metabolism
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Calcium Signaling* / drug effects
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Cell Membrane / enzymology
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Cells, Cultured
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Culture Techniques
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Cyclic ADP-Ribose
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Endothelin-1 / pharmacology*
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Endothelins / pharmacology
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Fluorescent Dyes / chemistry
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Inositol 1,4,5-Trisphosphate Receptors
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Male
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Membrane Glycoproteins
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Muscle Contraction* / drug effects
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Muscle, Smooth / drug effects
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Muscle, Smooth / physiology*
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Muscle, Smooth / ultrastructure
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NAD+ Nucleosidase / metabolism
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Peptide Fragments / pharmacology
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Rats
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Receptor, Endothelin B
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Receptors, Cytoplasmic and Nuclear / metabolism
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Receptors, Endothelin / agonists
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Ryanodine / metabolism
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Ryanodine / pharmacology
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Ryanodine Receptor Calcium Release Channel / analysis
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Seminiferous Tubules / cytology
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Seminiferous Tubules / physiology*
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Seminiferous Tubules / ultrastructure
Substances
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4,4-difluoro-4-bora-3a,4a-diaza-s-indacene
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Antigens, CD
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Antigens, Differentiation
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Boron Compounds
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Calcium Channels
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Endothelin-1
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Endothelins
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Fluorescent Dyes
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Inositol 1,4,5-Trisphosphate Receptors
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Membrane Glycoproteins
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Peptide Fragments
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Receptor, Endothelin B
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Receptors, Cytoplasmic and Nuclear
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Receptors, Endothelin
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Ryanodine Receptor Calcium Release Channel
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Cyclic ADP-Ribose
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sovateltide
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Ryanodine
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Adenosine Diphosphate Ribose
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ADP-ribosyl Cyclase
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Cd38 protein, rat
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NAD+ Nucleosidase
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ADP-ribosyl Cyclase 1