Ru-labeled ruthenocenoyl-glycine: comparison of clearance with hippuran.

Ruthenocenoyl-glycine (ruppuran) is a metallocene analog of iodo-labeled hippuran. After injection of 103Ru-labeled ruppuran and ruthenocenoyl-1,1'-diglycine in rabbits, measurement with external detectors revealed a very rapid accumulation in the kidneys followed by rapid excretion of the 103Ru activity. By measurement of the radioactivity concentration in plasma and urine samples collected 1-60 min after IV injection, the plasma clearance was calculated and compared with the clearance of 125I-labeled hippuran injected simultaneously. The clearance of ruppuran and ruthenocenoyl-diglycine in rabbits was found to be somewhat higher than that of hippuran. Extrapolating to man (1.73 m3), plasma clearance with both ruthenocene derivatives was approximately 500-600 ml/min. Biochemical data as well as the nuclear properties of 97Ru indicate the usefulness of 97Ru-labeled ruthenocenoyl-glycine as a radiopharmaceutical for kidney function studies.

Induced hyperosmolality effects on extracellular fluid volume, lymph flow and osmolar equilibrium: studies in the rat.

The effects of experimentally induced hyperosmolality has been studied in rats. Renal vascular pedicle ligation was performed on all animals to prevent renal clearance of the infused solute, xylose, and allow accurate ECF space determinations with 51Cr EDTA. Small volume hyperosmolar xylose infusions caused parallel elevation of the osmolality of thoracic duct lymph and arterial plasma. A positive correlation was obtained between lymph osmolality and flow alterations. The maximal osmolality elevation of 22 mosm X kg-1 H2O was associated with an intracellular fluid mobilisation which was equal to 7.1% of the ECF space. The infused and mobilised fluid volumes were distributed unequally between the intra and extra vascular compartments of the ECF.

In vitro uptake of bile acids by choroid plexus, kidney cortex and anterior uvea. I. The iodipamide-sensitive transport systems in the rabbit.

Renal cortex, anterior uvea, lateral choroid plexus and terminal ileum accumulate -14C-cholate, glycocholate, deoxycholate and chenodeoxycholate to considerable tissue/medium ratios. Iodipamide partly inhibits accumulation by kidney, uvea and plexus but not ileum. In renal cortex the sensitive part is similar to 10, 60 and 90 percent for dihydroxy acids, cholate and glycocholate respectively. Hippurate depresses uptake in kidney and uvea but hardly in plexus. Simultaneous uptake by renal cortex and uvea of -14C-cholate or glycocholate, -125I-iodipamide and -131I-o-iodohippurate was studied with unlabelled iodipamide and hippurate as inhibitors. The concentration-dependence of the inhibition required the assumption of 4 partly overlapping iodipamide-sensitive transport systems handling the 4 test substances: the hippurate (H)-system, one moderately (L(1)) and one very hippurate-resistant (L(2)) part of the liverlike L-system and a fourth system called BS, more evenly inhibitable by iodipamide and hippurate than the others. The L(2)-system carries iodipamide but very little bile acids. No iodipamide-sensitive system clearly specialized for bile acid transport was found. The systems have only moderate affinity for bile acids and probably treat them just as large organic anions. A new mathematical procedure to test the degree of complexity of composite transport systems without kinetic assumptions was used.