Relative contributions of Ca2+ mobilization and influx in renal arteriolar contractile responses to arginine vasopressin.
Experiments addressed the hypothesis that afferent and efferent arterioles differentially rely on Ca2+ influx and/or release from intracellular stores in generating contractile responses to AVP. The effect of Ca2+ store depletion or voltage-gated Ca2+ channel (VGCC) blockade on contractile responsiveness to AVP (0.01-1.0 nM) was assessed in blood-perfused juxtamedullary nephrons from rat kidney. Depletion of intracellular Ca2+ stores by 100 microM cyclopiazonic acid (CPA) or 1 microM thapsigargin treatment increased afferent arteriolar baseline diameter by 14 and 21%, respectively, but did not significantly alter efferent arteriolar diameter. CPA attenuated the contractile response to 1.0 nM AVP by 34 and 55% in afferent and efferent arterioles, respectively (P = 0.013). The impact of thapsigargin on AVP-induced afferent arteriolar contraction (52% inhibition) was also less than its effect on the efferent arteriolar response (88% inhibition; P = 0.046). In experiments probing the role of the Ca2+ influx through VGCCs, 10 microM diltiazem evoked a 34% increase in baseline afferent arteriolar diameter and attenuated the contractile response to 1.0 nM AVP by 45%, without significantly altering efferent arteriolar baseline diameter or responsiveness to AVP. Combined treatment with both diltiazem and thapsigargin prevented AVP-induced contraction of both vascular segments. We conclude that Ca2+ release from the intracellular stores contributes to the contractile response to AVP in both afferent and efferent arterioles but is more prominent in the efferent arteriole. Moreover, the VGCC contribution to AVP-induced renal arteriolar contraction resides primarily in the afferent arteriole.
Fallet
Rachel W
RW
Dept. of Cellular and Integrative Physiology, Univ. of Nebraska College of Medicine, 985850 Nebraska Medical Ctr., Omaha, NE 68198-5850, USA.
Ikenaga
Hideki
H
Bast
Joseph P
JP
Carmines
Pamela K
PK
D000818:Animals; D001127:Arginine Vasopressin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004110:Diltiazem / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009399:Nephrons / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019284:Thapsigargin / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007211:Indoles; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D001127:Arginine Vasopressin; D019284:Thapsigargin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000252:Calcium-Transporting ATPases; D004110:Diltiazem; D002118:Calcium; C000543:cyclopiazonic acid