Potential role of the renal tubule in fixing the level of plasma sulfoconjugated catecholamines in the dog.

Plasma levels of sulfoconjugated catecholamines in human subjects and in dogs are usually much higher than those of native amines. Their origins and the mechanism(s) involved in fixing their plasma concentrations are not well known; however, several lines of clinical evidences indicate a major role for the kidney. Thus this study was undertaken to measure the renal fractional excretion--used as an overall index of kidney mechanisms involved in the handling of catecholamines and their sulfoconjugates in the dog--and to look for any possible relationships between plasma concentration and urinary excretion. This was carried out in 36 anesthetized hydropenic mongrel dogs. The mean values of the renal fractional excretion of sulfoconjugated dopamine, norepinephrine, and epinephrine were shown to be statistically greater than 100%, suggesting a predominant secretion by the renal tubules of hydropenic dogs. Statistically significant correlations between plasma concentration and urinary excretion of sulfoconjugates--independent of blood pressure, cardiac output, clearance of para-aminohippuric acid, glomerular filtration rate, and sodium excretion are reported. Thus any change in the tubular handling of sulfoconjugates is likely to have a direct consequence in the fixation of their plasma concentrations.