Autoradiographic localization of 35-S-furosemide at different stages of its renal excretion.
The renal localization of 35-S-activity was studied by autoradiography at different times (1/2 min intervals) following the rapid injection of a bolus of 70 micrograms 35-S-furosemide into the renal portal system of hens. After removal, both kidneys were freeze-sectioned, freeze-dried and subjected either to apposition autoradiography according to Ullberg or to microautoradiography. There was extensive labelling over cortical areas of the ipsilateral kidney, in the periphery of lobuli, the site of proximal tubular cells. This labelling was maximal at 1 and insignificant already at 4 min post injection. At this time, however, there was a distinct patchy labelling corresponding to collecting ducts. At 7 min post-injection no specific labelling was found. The findings suggest that furosemide in the peritubular blood is accumulated in proximal tubules, rapidly transferred (tubular secretion) to their lumina and carried distally by the tubular fluid, subsequently resulting in high concentrations of the diuretic in the lumina of collecting ducts. Thus the findings are in keeping with the view that active tubular secretion of furosemide in the hen contributes significantly to a high luminal concentration of the drug in more distal parts of the tubules, the likely site of diuretic action.
D000818:Animals; D001345:Autoradiography; D002645:Chickens; D005260:Female; D005665:Furosemide / Q000652:urine*; D007668:Kidney / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D013997:Time Factors
D005665:Furosemide