Factors affecting the maturation of glomerular filtration rate and renal plasma flow in the new‐born dog

Abstract

SUMMARY1. The maturation of glomerular filtration rate was studied by comparison of thirty-six new-born mongrel dogs aged 1-35 days with six adult dogs.2. Under mannitol diuresis, glomerular filtration rate (GFR) rose from 0X 16 ml. min-'. g kidney-' at 1 day of age to 0 34 ml. min-'. g kidney-' at 1 month of age. Adult GFR averaged 0X68 ml. min-'. g-. There was good correlation of GFR with arterial blood pressure (r = 0-76, P < 0-001). Part of the statistical correlation of GFR with blood pressure was found to be independent of the relationship between blood pressure and age.3. Acute increases or decreases in blood pressure resulted in parallel changes in GFR in the puppies. There was no change of GFR with change of blood pressure in adult dogs. Carotid artery clamping, independent of blood pressure changes, produced increased renal vascular resistance and decreased GFR in the pups.4. Renal plasma flow (RPF) increased from 0 70 ml. min-'. g-' at 1 day of age to 1 80 ml. min-. g-1 at 1 month and showed good correlation with blood pressure (r = 0-67, P < 0-001). Filtration fraction (GFR/RPF) and renal vascular resistance did not vary with age in the pup and were the same as those for the adult.5. These results support the hypothesis that maturation of GFR and RPF are closely related to maturation of arterial blood pressure in the mongrel dog. The factors other than blood pressure which also affect renal maturation in the dog still need to be more clearly defined. LEONARD I. KLEINMAN AND RONALD J. LUBBE

Cerebrovascular Hemodynamics during and after Recovery from Acute Asphyxia in the Newborn Dog

“…There were no significant differences between individual pressure measurements in periods I, 111, and IV. The baseline (period I) MAP of 45.7 5 4.5 mm Hg is in agreement with previous experience in barbiturate anesthetized dogs of this age (8). By the end of the asphyxia (pre-11), MAP had fallen to 21.3 + 4.5 mm Hg ( p < 0.01 versus all other periods), but increased abruptly during recovery to peak at 69.6 + 6.0 mm Hg The CPP during the acute recovery (represented by the I1 results) was calculated as the peak MAP minus the peak SSP.…”

Effect of Acute Polycythemia on Newborn Renal Hemodynamics and Function

“…In control animals (Group I), there were no effects of exchange transfusion with adult whole blood on hematocrit or any of the physiologic functions studied ( Table 1). The values for arterial blood pressure, renal hemodynamics and renal function in control animals are similar to values reported in newborn puppies in earlier studies (8,9). Results of the experimental group (Group 11) are presented with the baseline determination as control values for each animal.…”

“…McDonald (11) studied the effect of altered blood viscosity on renal blood flow in adult dogs by altering hematocrit and found similar results. The renal vasodilatation in the puppies, however, is surprising in view of previous studies from our laboratory demonstrating that newborn dogs, in contrast to adult dogs, were unable to decrease renal vascular resistance and thus maintain renal blood flow when renal perfusion pressure was lowered (9). Thus mechanisms involved in maintaining blood flow in polycythemia appear to be different from those involved in hypotension.…”

“…Polycythemia was produced by an exchange tranfusion with adult dog packed red cells identical to that in the experimental group (Group 11). In these animals, in addition to the surgical procedures described above, a narrow bore polyethylene catheter (PE-10) was placed in the renal vein using techniques described in detail in a previous paper (9). Following injection of microspheres into the left ventricle, a sample of blood was collected from the renal vein for 3 min and the radioactivity counted.…”

Neuronal nitric oxide synthase, nNOS, regulates renal hemodynamics in the postnatal developing piglet

“…The newborn's renal hemodynamic state is characterized by high RVR, which results in low RBF (24)(25)(26). The major factor that causes the newborn's elevated RVR is enhancement of the RAS (2,9,11,27,28).…”