Intravenous delivery of PTH/PTHrP type 1 receptor cDNA to rats decreases heart rate, blood pressure, renal tone, renin angiotensin system, and stress-induced cardiovascular responses.
While parathyroid hormone type 1 receptor (PTH1R)-mediated vasodilatory, cardiac stimulatory, and renin-activating effects of exogenous PTH/PTH-related protein (PTHrP) are acknowledged, interactions of endogenous PTHrP with these systems remain unclear, mainly because the unavailability of viable PTHrP/PTH1R knockout mice. Transgenic mice overexpressing PTH1R in smooth muscle strongly have supported the PTHrP/PTH1R system as a cardiovascular system (CVS) regulator, but the consequences on renovascular (RVS) and renin-angiotensin systems (RAS) have not been explored in these studies. The aim was to develop a model in which one could study the consequences on CVS, RVS, and RAS of generalized PTH1R overexpression. Systemic PTH1R cDNA plasmid delivery was used in adult rats, a system that is amenable to studies in isolated perfused kidneys and that minimizes development-induced compensatory mechanisms. Intravenous administration of hPTH1R or green fluorescence protein-tagged hPTH1R in pcDNA3 resulted 3 wk later, in generalized expression of hPTH1R (mRNA and protein), especially in vessels, liver, heart, kidney, and central nervous system, where it is expressed physiologically. As expected, PTH1R overexpression decreased BP and renal tone. Unexpected, however, PTH1R overexpression decreased heart rate. These studies also revealed that endogenous PTHrP actually inhibits renin release and that hPTH1R overexpression tends to increase that effect. Striking, liver production and circulatory level of angiotensinogen and hence plasma renin activity were markedly reduced. Thus, abrupt PTH1R overexpression in adult rats profoundly alters the CVS, RVS, and RAS, strongly supporting the PTH/PTHrP/PTH1R system as crucial for heart and vascular tone regulation. In addition, these results revealed that PTH1R-mediated mechanisms might have protective effects against cardiovascular stress-induced responses, including stimulations in heart rate and RAS.
Renovascular Pharmacology and Physiology (INSERM), University of Louis Pasteur School of Medicine, Strasbourg, France.
Samuel
S
Fritsch
Veronique
V
Lindner
Sandra
S
Welsch
Thierry
T
Massfelder
Michele
M
Grima
Sylvie
S
Rothhut
Mariette
M
Barthelmebs
Jean-Jacques
JJ
Helwig
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001795:Blood Pressure Determination; D002319:Cardiovascular System / Q000187:drug effects*; D018076:DNA, Complementary / Q000032:analysis; D004195:Disease Models, Animal; D005260:Female; D005786:Gene Expression Regulation; D006339:Heart Rate / Q000187:drug effects*; D007275:Injections, Intravenous; D007677:Kidney Function Tests; D008297:Male; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000008:administration & dosage*; D012016:Reference Values; D012079:Renal Circulation / Q000502:physiology; D012084:Renin-Angiotensin System / Q000187:drug effects*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors
D018076:DNA, Complementary; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger; D044168:Receptor, Parathyroid Hormone, Type 1