THE RENAL CIRCULATION 



I 4 8; 



An ureterorenal reflex was described by Hix (146). 

 When a catheter distended the ureter in the dog, 

 ipsilateral plasma flow and GFR decreased. The 

 afferent stimulus facilitated further decrease in these 

 functions during emotional stimulus. Anesthetization 

 of the ureter or surgical denervation abolished the 

 reflex. The physiological significance of such viscero- 

 vascular reflexes is not apparent; but it can be sug- 

 gested that the circumstances evoking the reflex 

 (bladder distention, ureteral irritation) are such that 

 cessation of urine production would be beneficial, 

 at least temporarily. 



CENTRAL NERVOUS SYSTEM (CNS) CONTROL OF RENAL 



blood flow. Evidence exists that a representation of 

 control of the renal circulation exists in the cerebral 

 cortex. Smith (286) in 1940 presented an example of 

 psychogenic renal vasoconstriction, as evidenced by a 

 marked decrease in the Diodrast clearance; the inulin 

 clearance decreased only slightly, so that FF increased. 

 Meehan recently has confirmed the observation that 

 emotional states will cause a decrease in renal plasma 

 flow (PAH clearance) (200). Cort (66) observed 

 reduction of A-V oxygen and carbon dioxide differ- 

 ences in the cat kidney during stimulation of the 

 supraorbital cortex, signifying reduction in flow. 

 Hoff et al. (147) acutely stimulated two cortical foci 

 in cats on the right and left anterior sigmoid gyri, or 

 applied more diffuse chronic stimuli to the rostral 

 surface of the cranium. Ischemia of the renal cortex 

 (revealed by India ink injection) resulted, with little 

 effect on the renal medulla. When denervated, the 

 kidney was passively engorged as the blood pressure 

 rose. Chronic stimulation for a number of days led to 

 tubular degeneration as a result of the continued 

 ischemia. 



Wise & Ganong (350) stimulated the hypothala- 

 mus, pons, and medulla oblongata of pentobarbital- 

 ized dogs with chronically implanted electrodes. 

 Effects on glomerular filtration, and excretion of water 

 and electrolytes were studied. Influence on GFR was 

 variable: stimulation of the dorsal medulla just lateral 

 to the midline led to a rise in blood pressure with an 

 associated decline in GFR and urine volume, abol- 

 ished by renal denervation. Stimulation of an area in 

 the obex, in and near the area postrema, led to a rise in 

 GFR and urine volume, without significant change in 

 blood pressure. Other points stimulated in the brain 

 stem (medulla, pons, midbrain, and posterior hypo- 

 thalamus) had no effects on GFR and electrolyte 

 excretion, even though some stimuli caused changes 

 in blood pressure. 



Thus, the CNS control of the renal circulation is 

 intimately wrapped up in the general problems of 

 higher regulation of the cardiovascular system. As 

 these become worked out, better insight into renal 

 control will eventuate (241). 



Humoral Control ; Pharmacologic Agents 



adrenergic. /-Epinephrine and arterenol (levartere- 

 nol, norepinephrine) are both active vasoconstrictors 

 of the renal vasculature. The comparative potency, 

 and the site of action is not entirely settled, depending 

 upon technique employed, e.g., indirect clearance 

 techniques with intravenous injection, or direct flow 

 studies with intra-arterial injection. The latter 

 method, employed by Spencer et al. (292) has an 

 obvious advantage in that local effects can be ob- 

 served without demonstrable alteration of systemic 

 pressure. Flow measurement was made with an elec- 

 tromagnetic flowmeter in dogs. Table 7 shows the 

 effect of the same dosage of epinephrine and arterenol 

 as measured by the volume of blood shunted from the 

 kidney. Only at a 10 ng dose is the difference signifi- 

 cant, and at this dose epinephrine appears to be the 

 more effective. 



Werko et al. (335) compared the effects on clear- 

 ances (C In and C PAH ) done in man. The substances 

 were given in approximately the same dosage during 

 two experimental periods, following control. An 

 attempt to assess the differential site of action was 

 made by application of the formula of Gomez (105) 

 for calculation of regional vascular resistance. The 

 average values appear in table 8. 



As Spencer et al. found, the differences between the 

 action of these two adrenergic drugs are not great, and 

 here arterenol appears to be the more effective. For 

 both, the greatest degree of resistance change was in 

 the afferent arterioles. Maxwell et al. (199) injected 

 1.0 to 1.5 mg of epinephrine intramuscularly in 

 human subjects, and noted a decrease of 13 per cent 



TABLE 7. Effect of Epinephrine and Arterenol on 

 Renal Blood Flow in the Dog 



[After Spencer et al. (292).] 



