title: Transmembrane signalling of cholinergic-stimulated contraction in isolated rat glomeruli.
abstract: Exposure of isolated rat glomeruli to carbachol (Carb) 1 mM induces glomerular (mesangial cell) contraction which is inhibited by pirenzepine. To identify the cellular signalling mechanism, we analyzed Carb-activated phosphoinositide hydrolysis in myo-[2-3H] inositol preloaded cells of isolated rat glomeruli. Carb evoked a rapid (5 s, 30.4 +/- 8.3% of basal) and sustained (60 s, 157.2 +/- 1.2% of basal) inositol trisphosphate (IP3) response. Acetylcholine 100 microM (Ach) in the presence of eserine also evoked IP3 formation. Mobilization of Ca2+ was monitored by preloading glomerular cells with 45Ca2+ (200 microCi/ml) and analyzing the cellular efflux using a constant perifusion system. Both Carb and Ach induced transient 45Ca2+ efflux, with peak values above baseline of 69.0 +/- 19.9 and 71.5 +/- 7.9%, respectively. Incubation with pirenzepine or prior release of Ca2+ from an IP3-sensitive intracellular pool by Thapsigargin (2 microM) prevented Carb-evoked Ca2+ release (100 and 60%, respectively). Therefore, glomerular cells possess functional cholinergic receptors which stimulate contraction via IP3-mediated intracellular Ca2+ release.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology*; D002413:Cations, Divalent; D002462:Cell Membrane / Q000378:metabolism; D004347:Drug Interactions; D005920:Glomerular Mesangium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000096:biosynthesis; D007678:Kidney Glomerulus / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008297:Male; D010830:Physostigmine / Q000494:pharmacology; D010890:Pirenzepine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011950:Receptors, Cholinergic / Q000378:metabolism; D015398:Signal Transduction; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
chemical_list: D002413:Cations, Divalent; D007295:Inositol Phosphates; D011950:Receptors, Cholinergic; D013729:Terpenes; D010890:Pirenzepine; D019284:Thapsigargin; D002217:Carbachol; D010830:Physostigmine; D000109:Acetylcholine; D002118:Calcium