Abnormal renovascular parathyroid hormone-1 receptor in hypertension: Primary defect or secondary to angiotensin ii type 1 receptor activation?
We previously reported that PTHrP-induced renal vasodilation is impaired in mature spontaneously hypertensive rats (SHR) through down-regulation of the type 1 PTH/PTHrP receptor (PTH1R), a feature that contributes to the high renal vascular resistance in SHR. Here we asked whether this defect represents a prime determinant in genetic hypertension or whether it is secondary to angiotensin II (Ang II) and/or the mechanical forces exerted on the vascular wall. We found that the treatment of SHR with established hypertension by the Ang II type 1 receptor antagonist, losartan, reversed the down-regulation of PTH1R expression in intrarenal small arteries and restored PTHrP-induced vasodilation in ex vivo perfused kidneys. In contrast, the PTH1R deregulation was not found in intrarenal arteries isolated from prehypertensive SHR. Moreover, this defect, which is not seen in extrarenal vessels (aorta, mesenteric arteries) from mature SHR appeared kidney specific in accordance with the acknowledged enrichment of interstitial Ang II in this organ and its enhancement in SHR. In deoxycorticosterone-acetate-salt rats, an Ang II-independent model of hypertension, renovascular PTH1R expression and related vasodilation were not altered. In SHR-derived renovascular smooth muscle cells (RvSMCs), the PTH1R was spontaneously down-regulated and its transcript destabilized, compared with Wistar RvSMCs, both effects being antagonized by losartan. Exogenous Ang II elicited down-regulation of PTH1R mRNA in RvSMCs from Wistar rats. Together, these data demonstrate that Ang II acts via the Ang II type 1 receptor to destabilize PTH1R mRNA in the renal vessel in the SHR model of genetic hypertension. This process is kidney specific and independent from blood pressure increase.
Welsch
Sandra
S
Institut National de la Santé et de la Recherche Médicale, Unité 727, Strasbourg F-67085 France.
Schordan
Eric
E
Coquard
Catherine
C
Massfelder
Thierry
T
Fiaschi-Taesch
Nathalie
N
Helwig
Jean-Jacques
JJ
Barthelmebs
Mariette
M
D000804:Angiotensin II / Q000494:pharmacology / Q000502:physiology*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000737:chemistry / Q000378:metabolism; D002478:Cells, Cultured; D003900:Desoxycorticosterone; D015536:Down-Regulation / Q000187:drug effects; D006973:Hypertension / Q000139:chemically induced / Q000188:drug therapy / Q000235:genetics*; D007668:Kidney / Q000098:blood supply*; D019808:Losartan / Q000627:therapeutic use; D008297:Male; D044162:Parathyroid Hormone-Related Protein / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011918:Rats, Inbred SHR; D017208:Rats, Wistar; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology*; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014664:Vasodilation / Q000187:drug effects
D047228:Angiotensin II Type 1 Receptor Blockers; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044168:Receptor, Parathyroid Hormone, Type 1; D000804:Angiotensin II; D003900:Desoxycorticosterone; D019808:Losartan