Governance of arteriolar oscillation by ryanodine receptors.
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.
Takenaka
Tsuneo
T
Dept. of Medicine, Nephrology Division, Saitama Medical College, 38 Moro-hongo Moroyama, Iruma, Saitama 350-0495, Japan.
Ohno
Yoichi
Y
Hayashi
Koichi
K
Saruta
Takao
T
Suzuki
Hiromichi
H
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*
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