Maturation of glomerular blood flow distribution in the new‐born dog

Abstract

SUMMARY1. Glomerular blood flow distribution was studied in seventy-eight new-born mongrel dogs aged 1-40 days by measuring the distribution of radioactive labelled microspheres within the kidney.2. The microsphere technique was found to be a valid indicator of glomerular blood flow distribution for the new-born dog since (a) the spheres were completely extracted by the kidney, (b) more than 95 % of the spheres were trapped in glomerular capillaries, (c) the spheres were evenly distributed within any specific region of the kidney and, (d) the spheres did not interfere with renal haemodynamics.3. Plasma flow per gram tissue to inner cortical glomeruli, relative to that to outer cortical glomeruli, the IC/OC flow ratio, was high at birth, decreased over the first 2 weeks of life and remained relatively constant thereafter. Plasma flow per gram tissue to the outer cortex increased over the whole 40 day period while that to the inner cortex decreased slightly and then increased after 2 weeks.4. The IC/OC flow ratio decreased in a curvilinear fashion as blood pressure rose with maturation. Acute increases or decreases in blood pressure in any animal produced decreases or increases, respectively, in the IC/OC flow ratio.5. There was no correlation between the IC/OC flow ratio and renal extraction of p-amino-hippurate (EPAH)-6. There was histological evidence that glomerular differentiation persists for 2 weeks during the post-natal period in the dog. This continuing post-natal glomerulogenesis takes place only in the outer cortex.7. These results are consistent with the hypothesis that an important factor in renal maturation is a redistribution of blood flow within the kidney. As the animal matures a greater fraction of the total glomerular blood flow goes to outer cortical glomeruli. This is due partly to the 92 LEONARD I. KLEINMAN AND JOHN H. REUTER continuing glomerular differentiation taking place in the outer cortical region and partly to the increasing arterial blood pressure occurring with maturation.

Ontogeny of Single Glomerular Perfusion Rate in Fetal and Newborn Lambs

“…of age. The present study demonstrates for the first time in lambs that the nephrogenic zone disappears around 130 days of gestation and that the total glomerular counts per kidney in fetuses over Previous studies (5,13,14,16) have demonstrated that the 130 days (4682% + 41173 glomeruli per kidney) is not significantly cortical blood flow is distributed preferentially to the juxtameduldifferent than in newborn lambs (433704 + 21553). Glomerular lary area of the cortex during early postnatal life, and with density, determined in four cortical zones (zone I being the out-maturation, the development of cortical flow follows a centrifugal ermost portion of the cortex) did not show any significant changes pattern.…”

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.…”

“…The kidneys were removed from the animal, weighed, allowed to dry overnight and then weighed and placed in a Packard auto gamma spectrometer and the radioactivity counted. These methods have been described in detail in an earlier paper (8). Although a relatively narrow range of spectral activity for-each isotope was chosen, complete separation of the isotopes was not achieved and crossover between the different isotopes was resolved by simultaneous equations.…”

“…Furthermore, 8% of newborn infants have hematocrits greater than 65% and may have problems related to the effects of polycythemia and altered viscosity (6,17). There are also differences in renal function and renal hemodynamics between the newborn and adult animal (8), so that results of experiments dealing with effects of changing hematocrit on renal hemodynamics and function in adult animals may not necessarily apply to the newborn animal. For these reasons, the effects of increasing hematocrit on renal hemodynamics in a newborn animal model were studied.…”

p-Aminohippurate Transport in the Proximal Straight Tubule: Development and Substrate Stimulation

“…It has been clearly established that renal growth (10,12,19,20,23) and functional maturation (2,13,14,17,22) proceed centrifugally. This is associated with the development of a progressively more superficial population of nephrons, and presents a potential obstacle to the investigation of maturation at the single nephron level.…”