THE RENAL CIRCULATION 



I487 



which control peripheral resistance and venous return 

 and hence prevent the rise in blood pressure which 

 results from such maneuvers as clamping the carotids, 

 cutting the pressoreceptor nerves, the Valsalva maneu- 

 ver, and the cold pressor test. Essentially, they elimi- 

 nate efferent nervous influences which keep blood 

 pressure up. The fall in blood pressure which results 

 from their administration may, in part, be due to 

 decrease in cardiac output. Peripheral vasodilatation 

 and increased flow may occur, e.g., in the limbs, in 

 the presence of a fall in blood pressure, or at least 

 in the absence of a rise. There appears to be little or 

 no direct effect on the vasculature. Responses of the 

 splanchnic organs, including the kidney, may be quite 

 different: decreased blood pressure is accompanied by 

 decrease in flow. 



Hexamethonium chloride. Mover et al. (225) gave 2 

 to 5 mg per kg (iv) and observed an average drop 

 of 1 38 to 97 mm Hg in the blood pressure in 20 dogs 

 anesthetized with pentobarbital or chloralose. Glo- 

 merular filtration rate showed no change (46-45 

 ml min), RPF decreased from 182 to 1 72 ml per min, 

 and FF varied from 0.26 to 0.28. Renal vascular 

 resistance (RVR) decreased from 0.57 to 0.48, and 

 Tm G showed little alteration (161 -155 mg/'min). 



In patients (220), with a greater fall in blood pres- 

 sure at the dosage used, blood pressure fell to 66 

 per cent of control. C In decreased to 78 per cent, and 

 CTpah was maintained at 98 per cent of control, signify- 

 ing decrease in RYR. One must consider the possibil- 

 ity that renal autonomy may account for this, rather 

 than dilatation due to drug action. In another series, 

 in normotensive and hypertensive patients (209), 

 blood pressure decreased to 80 to 85 per cent of con- 

 trol following dosage of 5 to 75 mg. In half no change 

 or actual increase in RVR occurred, so that GFR and 

 RPF were reduced at the time of maximum decrease of 

 blood pressure. In the other half, RYR decreased so 

 that GFR and RPF were maintained despite the fall 

 in blood pressure. There was no effect on E PAS . 



Arjonad (trimethaphan camphorsulfonate) has a 

 greater depressing effect on renal function (GFR and 

 RPF) than hexamethonium, due to greater reduction 

 of blood pressure (227); RYR is not significantly 

 altered in normals. In patients with nephrosclerosis 

 (243) Cp AH , originally reduced, tended to be main- 

 tained despite a fall in blood pressure to 40 to 50 per 

 cent of control; C?i n was noticeably reduced. The 

 intensity of renal vasoconstriction in dogs, produced 

 by clamping the aorta or limb trauma, was relieved 

 by Arfonad blockade (26). 



Other blocking agents. Pendiomid (azamethonium 



chloride), administered to patients with no vascular 

 disease at the rate of 2 to 6 mg per min for several 

 hours (avg 250 mg over 3 hours), caused blood pres- 

 sure to fall from 97 to 71 mm Hg. Renal blood flow 

 decreased in about the proportion of the decline in 

 blood pressure, with no significant change in RVR 

 (228). Ecolid (chlorisondamine) in hypertensives 

 shows maintained renal blood flow despite significant 

 fall in blood pressure (77). Tetraethylammonium 

 bromide is a renal vasoconstrictor, according to Aas 

 & Blegen ( 1 ) as revealed by the more marked fall in 

 Cpah than systemic pressure. Priscoline (tolazoline), 

 state Young et al. (353), is a vasodepressor and a renal 

 constrictor both in humans and dogs. Marked decre- 

 ment in GFR occurs, along with somewhat lesser 

 decrease in RPF, and they believe the major site of 

 action is on the afferent arterioles. After denervation 

 of the kidney, Priscoline has no effect, and Young 

 and his group suggest that the drug causes afferent 

 arteriolar stimulation via the sympathetic innervation. 

 Ilidar (azapetine) directly injected into the renal 

 artery has no effect up to a dose of 3 mg; above this, 

 it is a constrictor (292). Regitine (phentolamine) 

 is both vasodepressor and vasodilator in dogs (226) 

 at infusion rates of 3 mg/kg for over 5 min RBF 

 increased from 307 to 341 ml per min, despite a de- 

 cline in blood pressure from 134 to 102 mm Hg. 

 Dibenzyline (phenoxybenzamine) was injected into 

 one renal artery of the dog, followed by infusion of 

 arterenol systemically. Marked decrease in GFR 

 and RPF occurred in the untreated kidney, but not 

 in the treated kidney (129). Dibenamine (N,n'- 

 dibenzyl-B-chloroethylamine hydrochloride) caused 

 definite remission of enhanced vasomotor tone result- 

 ing from hemorrhage in dog (34), but did not alter 

 the outcome of hemorrhagic shock. 



other vasoactive drugs. Apresoline (hydralazine) is 

 a vasodepressor which reduces vascular resistance in 

 the kidney. It is not a ganglionic blocker, but its exact 

 mechanism of action is unknown, although it has been 

 suggested that it may antagonize neurohumoral sub- 

 stances (such as serotonin, pherantosin, and angio- 

 tensin) which are believed to affect blood pressure. 

 Table g shows its effects in normal subjects and acute 

 nephritics (dosage, 0.2-2.5 mg/kg, orally). 



While improving normal blood flow, Apresoline 

 unaccountably increased vascular resistance of the 

 nephritics, despite a fall in systemic pressure. That 

 hypertension per se was not basic to this response is 

 shown by the effects in essential hypertensives studied 

 by Gjorup & Hilden (101). While mean blood pres- 



