Evaluation of the single nephron glomerular filtration coefficient in the dog

Influence of Bradykinin and Papaverine on Renal and Glomerular Hemodynamics in Dogs

“…However, studies have failed to indicate that K, values in the dog are lower at reduced arterial pres sures than at spontaneous arterial pressures [14][15][16][17][18]. Furthermore, recent studies have demonstrated that the administration of an tagonists of the renin-angiotensin system to either normal or sodium-restricted dogs also maintained at reduced renal arterial pres sure does not increase Kr significantly [14,25]. Therefore, it is unlikely that our control Kr values were already reduced due to the experimental conditions.…”

“…Such a mecha nism has been postulated to exist in the rat and it has been suggested that many agents exert their influence to reduce K, via a com mon pathway involving angiotensin II [24], To the extent that this phenomenon oc curred in our experiments it might be ex pected that K, was already reduced during our control conditions due to an increased local activity of angiotensin II. However, studies have failed to indicate that K, values in the dog are lower at reduced arterial pres sures than at spontaneous arterial pressures [14][15][16][17][18]. Furthermore, recent studies have demonstrated that the administration of an tagonists of the renin-angiotensin system to either normal or sodium-restricted dogs also maintained at reduced renal arterial pres sure does not increase Kr significantly [14,25].…”

“…As stated, the present experiments were performed at a reduced level of renal arterial pressure in order to minimize the possible overestimations of GP and SNGFR that might occur as a consequence of feedbackmediated allèrent arteriolar vasodilation during interruption of flow to the distal nephron [14][15][16]21], In addition, this al lowed us to conduct the measurements dur ing the control and vasodilator periods at equivalent renal arterial pressures. Under these circumstances, it is possible that there was an increased intrarenal formation of angiotensin II during the control periods leading to reductions in K,.…”

“…The results of experi ments performed on rats [11,12] have sug gested that several vasodilators induce marked decreases in the glomerular filtra tion coefficient (Kf) which counteract the influence of increases in plasma flow [13]. However, it has not been determined if such an effect occurs in dogs, a species in which Kf appears to be less responsive to various ma nipulations, and glomerular filtration dy namics are not characterized by filtration equilibrium [14][15][16][17][18][19], Thus, experiments were conducted to evaluate the effects of renal intra-arterial infusions of two com monly used vasodilator agents, bradykinin and papaverine, on glomerular filtration dy namics of dogs. These two agents were cho sen since bradykinin usually results in un changed GFR [4,5,[8][9][10] while papaverine mav actually cause decreases in GFR [2,3,6],…”

“…The dogs were anesthetized with sodium pentobarbital (30mg/kg body weight) and prepared for micropuncture and clearance studies as described previously [14][15][16]. The left jugularvein was catheterized to infuse a 5% inulin solution at a rate sufficient to establish a plasma inulin concentration of approximately 0.8 mg/ml.…”