Local effect of serotonin on renal vascular resistance and urine flow rate

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Abstract
The effect of serotonin upon renal vascular resistance and urine flow rate when infused directly into the renal artery was studied in 37 laparotomized anesthetized dogs. Concentrations of 10 and 100 µg/min. were utilized in kidneys that were innervated, denervated and denervated plus infused with a sympatholytic and adrenolytic agent. In one series, blood flow rate was maintained constant with a pump interposed in the renal artery. Pressures were measured in the renal artery and vein. Changes in renal vascular resistance in nerve intact, denervated and denervated phentolaminized kidneys were +0.14 ± 0.14, +0.16 ± 0.11 and +0.09 ± 0.07 mm Hg/ml/min. Urine flow rate did not change. In a second series, urine flow rate and aortic pressure were measured without the blood pump. Urine flow rate changes for intact, denervated and denervated phentolaminized kidneys were –0.30 ± 0.43, –0.06 ± 0.44 and 0.00 ± 0.37 ml/min. Aortic pressure remained constant. These data indicate that the local effect of serotonin in the amount used is to actively increase the geometric component of renal vascular resistance through some mechanism unrelated to extrinsic nerves and circulating or locally released catecholamines. Under the conditions of the study, regular changes in urine flow rate were not observed.