title: Governance of arteriolar oscillation by ryanodine receptors.
abstract: To investigate the role of ryanodine receptors in glomerular arterioles, experiments were performed using an isolated perfused hydronephrotic kidney model. In the first series of studies, BAYK-8644 (300 nM), a calcium agonist, constricted afferent (19.6 +/- 0.6 to 17.6 +/- 0.5 microm, n = 6, P < 0.01) but not efferent arterioles. Furthermore, BAYK-8644 elicited afferent arteriolar oscillatory movements. Subsequent administration of nifedipine (1 microM) inhibited both afferent arteriolar oscillation and constriction by BAYK-8644 (to 19.4 +/- 0.5 microm). In the second group, although BAYK-8644 constricted afferent arterioles treated with 1 microM of thapsigargin (19.7 +/- 0.6 to 16.8 +/- 0.6 microm, n = 5, P < 0.05), it failed to induce rhythmic contraction. Removal of extracellular calcium with EGTA (2 mM) reversed BAYK-8644-induced afferent arteriolar constriction (to 20.0 +/- 0.5 microm). In the third series of investigations, ryanodine (10 microM) but not 2-aminoethoxyphenyl borate (100 microM) abolished afferent arteriolar vasomotion by BAYK-8644. In the fourth series of experiments, in the presence of caffeine (1 mM), the stronger activation of voltage-dependent calcium channels by higher potassium media resulted in greater afferent arteriolar constriction and faster oscillation. Our results indicate that L-type calcium channels are rich in preglomerular but not postglomerular microvessels. Furthermore, the present findings suggest that either prolonged calcium influx through voltage-dependent calcium channels (BAYK-8644) or sensitized ryanodine receptors (caffeine) is required to trigger periodic calcium release through ryanodine receptors in afferent arterioles.
authors.affiliation: Dept. of Medicine, Nephrology Division, Saitama Medical College, 38 Moro-hongo Moroyama, Iruma, Saitama 350-0495, Japan.
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Takenaka
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ohno
authors.forename: Koichi
authors.initials: K
authors.lastname: Hayashi
authors.forename: Takao
authors.initials: T
authors.lastname: Saruta
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Suzuki
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000502:physiology; D001896:Boron Compounds / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006869:Hydronephrosis / Q000503:physiopathology; D007678:Kidney Glomerulus / Q000098:blood supply* / Q000502:physiology*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010507:Periodicity; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000502:physiology*; D019789:Tetraethylammonium / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D001896:Boron Compounds; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D010726:Phosphodiesterase Inhibitors; D026902:Potassium Channel Blockers; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D010042:Ouabain; D019789:Tetraethylammonium; D019284:Thapsigargin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; C109986:2-aminoethoxydiphenyl borate; D009543:Nifedipine; D002118:Calcium