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HANDBOOK OF PHYSIOLOGY 



ClkCILATION II 



vagus apparently contains no vasomotor fibers to the 

 kidney, and no evidence exists for vasodilator fibers 

 in this circuit. Hence, the vasomotor status of the 

 kidney is maintained by variations in vasoconstrictor 

 tone. 



the question of renal autonomy. Considerable 

 controversy has revolved around the question of 

 whether or not a continued flow of impulses passes 

 to the arterioles, or whether such regulation is absent 

 in the basal state, to be invoked only in emergency 

 states of heightened sympathetic nervous system 

 activity. Early investigators, working in anesthetized 

 animals, appeared to demonstrate a "denervation 

 hyperemia." In view of the fact that ample evidence 

 exists that morphine, ether, chloroform, urethane, and 

 pentobarbital anesthesia depress renal blood flow 

 to varying degrees, probably due to enhanced activity 

 of the sympathetic system and adrenal medulla, it is 

 understandable that removal of the neurogenic source 

 of renal vasoconstrictor activity would result in a 

 relative hyperemia, e.g., with unilateral denervation. 

 Earlier work in this area has been reviewed by Smith 

 (287) and Carstensen & Holle (51). 



When clearance techniques are employed in 

 trained, unanesthetized dogs, which have recovered 

 well from the effects of surgical denervation of one 

 kidney, or denervation and transplantation of one 

 organ, function is equal in the experimental and con- 

 trol kidneys. This includes concordance of glomerular 

 filtration rate (creatinine or inulin clearance), plasma 

 flow (Diodrast or PAH clearance), and indeed, diure- 

 tic activity and electrolyte excretion (17, 35, 139, 



197. 2 57> 2 99)- 



Carstensen & Holle (51) performed sympathetec- 



tomies at the levels of the first and second lumbar 

 vertebrae (Li and L2) in patients suffering with 

 arteriosclerotic obliterans and endarteritis obliterans. 

 Clearances of phenolsulfonphthalein (PSP), creati- 

 nine, and PAH were measured before and after the 

 operation. Although individual results were quite 

 variable, the average changes were not significant: 

 endogenous creatinine clearance for glomerular 

 filtration rate (GFR), 127 ± 42 before; 136 ± 59, 

 after; PAH clearance, 340 ±67 before; 366 ± 92 

 after. Unilateral sympathectomy (from T8 to Li, 

 and greater and lesser splanchnics) in patients with 

 essential hypertension did not increase blood flow 

 on the operated side (104), and both kidneys re- 

 sponded by an equal reduction in flow after Adrenalin 

 administration. 



Smith et al. (285) demonstrated in normal, un- 



operated human subjects that spinal anesthesia up 

 to T5 or higher did not produce renal hyperemia as 

 measured by the Diodrast clearance, nor did it have 

 any other consistent effect on the renal circulation. 

 They concluded that the renal blood flow is normally 

 determined by autonomous, intrinsic activity of the 

 renal arterioles and is not dependent upon the tonic 

 activity in the sympathetic pathways, which show 

 continued action potentials (263). 



It must be emphasized that despite its inherent 

 autonomy of circulation, the kidney will respond with 

 vasoconstriction during enhanced activity resulting 

 from direct electrical stimulation of the renal nerves 

 in the dog, rabbit, cat, and rat (81, 148, 167, 222, 

 298, 319); this is reversed by a variety of sympatholytic 

 drugs (81, 319). Studies of blood distribution in the 

 rabbit kidney supplemented with India ink injection 

 techniques, revealed that the resulting ischemia was 

 largely cortical, and that the blood supply to the 

 medullary zones was not noticeably altered (25). 

 Houck (148) examined the effect of electrical stimu- 

 lation of the renal nerves of anesthetized dogs on 

 blood flow (PAH clearance), filtration rate (creatinine 

 clearance), and Tm (tubular maximum) of PAH and 

 glucose (G). By relating filtration rate to unit of 

 tubular excretory tissue (filtration/Tm PAH ), and 

 reabsorptive tissue (filtration/Tm G ), and the per- 

 fusion of active tubules with blood (RBF/Tm PAH , 

 it was discerned that regions of ischemia were pro- 

 duced, with random closure of nephrons. This was 

 verified by the distribution of India ink injected into 

 the renal artery. The evidence was that the effects 

 resulted predominantly from constriction of the af- 

 ferent arterioles. Blood was not shunted from the 

 cortex to the medulla. Study & Shipley (298) also 

 believe the effects are largely on the afferent arterioles. 

 They too found no evidence of shunting. 



Strong afferent stimulation (acute tracheal com- 

 pression, sudden clamping of an upper or lower 

 extremity, and sciatic nerve stimulation (25, 65, 

 66) ) likewise caused renal vasoconstriction on a 

 reflex basis. Pain caused by intense cold stimulation 

 of the hand, or pressure headaches, resulted in de- 

 creased clearance of Diodrast and of inulin to a lesser 

 degree (filtration fraction increased), while blood 

 pressure increased (35 1 ) . 



More subtle reflex mechanisms have been dis- 

 cerned. Bladder distention in chloralosed cats gave 

 reflex increases in blood pressure; apparently the 

 kidney participated in the vasoconstriction as mani- 

 fested by decreases in volume (229). Bilateral splanch- 

 nectomy abolished the viscerovascular response. 



