[Renal vasodilator effect of parathormone].
Parathyroid hormone (PTH) has been shown to decrease blood pressure in several animal species and to increase blood flow in different vascular beds. The aim of this work was to characterize and quantify the renal vasodilator effect of PTH on the isolated perfused kidney of the rat. The rat kidney was isolated and perfused in a closed circuit with a modified Krebs-Henseleit solution under non filtering conditions (BSA 10 g/100 ml, ligature of the ureter and perfusion pressure set on 70 mmHg). These conditions have been shown to avoid both glomerular filtration and PTH degradation. Vascular tone of the isolated kidney was restored by a continuous perfusion of prostaglandin F2 alpha (2 x 10(-8) mol/mn). The vasodilator responses to PTH were expressed as a percentage of the relaxation induced on each kidney preparation by 4.4 x 10(-4) M papaverine. PTH fragments [bovine PTH (1-34), NLe8.18Tyr34bPTH (1-34) amide and rat PTH (1-34)] induced concentration-dependent renal vasodilation. When tested at increasing cumulative concentrations, EC50 values ranged from 1 to 2 nM for all PTH fragments; maximal relaxation was obtained at 10(-8) M and only approached 40 p. 100 of the response induced by papaverine. Moreover, at concentrations higher than 10(-8) M, all three peptides induced lower vasodilator responses. Neither indomethacin nor phentolamine modified rPTH (1-34) induced renal response. When rPTH (1-34) was tested as a single concentration on each kidney preparation, a higher maximal response (60 p. 100 relaxation) was obtained. This suggested tachyphylaxis of the renal vasculature to repeated PTH administration.(ABSTRACT TRUNCATED AT 250 WORDS)
Musso
M J
MJ
Institut de pharmacologie, URA DO 589 CNRS, faculté de médecine, université Louis-Pasteur, Strasbourg, France.
Barthelmebs
M
M
Helwig
J J
JJ
Imbs
J L
JL
D000818:Animals; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects*; D008297:Male; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012077:Renal Artery / Q000187:drug effects; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology*
D010281:Parathyroid Hormone; D010446:Peptide Fragments; D014665:Vasodilator Agents
Action vasodilatatrice rénale de la parathormone.