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Biomedical subjects

R H Bowman

Publications and source records attributed to R H Bowman.

At least 19 recordsLinked to original sources
PubMed1978

The effects of 2,4,6-triaminopyrimidine (TAP) on sodium and potassium excretion by the rat kidney: comparison with amiloride.

2,4,6-Triaminopyrimidine (TAP) has been reported to be a blocker of the cation-specific paracellular conductance pathways of several epithelia. The compound is also known to inhibit sodium transport in the frog skin. Its effects on renal function were studied in clearance experiments in anesthetized rats and in isolated perfused rat kidneys and compared with the effects of amiloride. The effects of both compounds on electrical resistance of the frog gallbladder were also evaluated. Both TAP and amiloride caused modest natriuresis and a marked reduction in potassium excretion. Amiloride is approximately 1000 times more potent than TAP when compared on the basis of drug concentration in the urine. The concentrations of both substances in urine (at effective doses) correspond to concentrations reported to be effective against sodium transport in amphibian membranes. The urinary concentrations of TAP also correspond to the concentrations required to inhibit paracellular cation movement in the gallbladder. Amiloride at the level tested (10(-3) M) did not seem to influence the paracellular pathway. The results neither establish nor disprove a role of the paracellular pathway in potassium secretion. Both TAP and amiloride are secreted by the renal tubules.

Amiloride↗
PubMed1975

Renal secretion of [35-S]furosemide and depression by albumin binding.

It was determined by use of [35-S]furosemide and an ultrafiltration procedure that furosemide is bound extensively to bovine serum albumin. When 500 muM furosemide and albumin at a concentration of 2.5 g/100 ml were used, approximately 90% of the drug was bound. With this same amount of furosemide, but with 3 times as much albumin, binding was about 98%. Using a 25-fold lower concentration of furosemide, 20 muM, binding was nearly 98% with 2.5 g albumin/100 ml, and was over 98% with 7.5 g albumin/100 ml. These same concentrations of furosemide and albumin were used to investigate the excretory and secretory rates of [35-S]furosemide in the isolated perfused rat kidney. Tubular clearance (i.e., secretion) of [35-S]furosemide was inversely related to the concentration of albumin in the perfusate. In kidneys perfused without albumin, tubular clearance of the drug was 6-20 times that found when 2.5 or 7.5 g albumin/100 ml, respectively, was used. Probenecid, with or without albumin, reduced the clearance of furosemide to that of its filtration rate. It is concluded that at physiological albumin concentrations, a very small fraction of circulating furosemide will be available for filtration, and tubular-fluid and urinary furosemide will arise predominantly from secretion. Because of extensive binding of furosemide to albumin, the renal secretory process itself is depressed, and the rate of secretion will be dependent, in part, on the concentration of unbound drug.

Aminohippuric Acids↗