Knockdown of parathyroid hormone related protein in smooth muscle cells alters renal hemodynamics but not blood pressure-

Authors
D. Raison, C. Coquard, M. Hochane, J. Steger, T. Massfelder et al

Lab
INSERM U682, Equipe Cancer du rein et Physiopathologie rénale, Strasbourg, France;

Journal
American Journal of Physiology - Renal Physiology

Abstract
Parathyroid hormone related protein (PTHrP) belongs to vasoactive factors that regulate blood pressure and renal hemodynamics both by reducing vascular tone and raising renin release. PTHrP is expressed in systemic and renal vasculature. Here we wanted to assess the contribution of vascular smooth muscle cell endogenous PTHrP to the regulation of cardiovascular and renal functions. We generated a mouse strain (SMA-CreERT2/PTHrPL2/L2 or premutant PTHrPSM-/-) which allows temporally-controlled, smooth muscle targeted PTHrP knockdown in adult mice. Tamoxifen treatment induced efficient recombination of PTHrP floxed alleles, and decreased PTHrP expression in vascular and visceral smooth muscle cells of PTHrPSM-/- mice. Blood pressure remained unchanged in PTHrPSM-/- mice, but plasma renin concentration and creatinine clearance were reduced. Renal hemodynamics were further analyzed during clearance measurements in anaesthetized mice. Conditional knockdown of PTHrP decreased renal plasma flow and glomerular filtration rate with concomitant reduction in filtration fraction. Similar measurements were repeated during acute saline volume expansion. Saline volume expansion induced a rise in renal plasma flow and reduced filtration fraction; both were blunted in PTHrPSM-/- mice leading to impaired diuresis. These findings show that endogenous vascular smooth muscle PTHrP controls renal hemodynamics under basal conditions, and is an essential factor in renal vasodilation elicited by saline volume expansion.

BIOSEB Instruments Used:
Non Invasive Pressure Measurement (LE5001),Non Invasive Pressure Measurement (LE5007)