[3H]netilmicin binding constants and phospholipid composition of renal plasma membranes of normal and diabetic rats.
We examined the hypothesis that the decreased renal accumulation of aminoglycosides in rats with streptozotocin-induced diabetes mellitus is due to decreased membrane binding of drug consequent to reduced membrane content of the putative aminoglycoside receptor, phosphatidylinositol. Renal brush border membrane (BBM) and basolateral membrane (BLM) vesicles were prepared from normal and diabetic Sprague-Dawley rats by differential centrifugation and Percoll gradient techniques which yielded relatively pure membrane fractions as assessed by measurements of marker enzymes and by electron microscopy. Binding of [3H]netilmicin to plasma membranes was performed using a fast filtration technique. Scatchard analysis of the binding data indicated that netilmicin bound to a single class of receptors on BBM and BLM from normal rats with an affinity constant of 33 +/- 2 X 10(3)M-1 and 23 +/- 2 X 10(3)M-1, respectively. The maximal binding capacity of BLM (70 +/- 4 nmol/mg of protein) was significantly greater (P less than .01) than that of BBM (38 +/- 1 nmol/mg of protein). The affinity constants and maximal binding capacities of BBM and BLM from diabetic rats were not significantly different from those of normal rats. Moreover, 2 days of gentamicin injections at 100 mg/kg/day for 2 days had no appreciable effect on these binding parameters in either group. In control rats the total phospholipid content of BLM (785 +/- 19 nmol/mg of protein) was significantly greater (P less than .01) than that of BBM (592 +/- 19 nmol/mg of protein) and reflected significantly greater quantities of sphingomyelin, phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005839:Gentamicins / Q000378:metabolism* / Q000494:pharmacology; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism*; D009428:Netilmicin / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D005839:Gentamicins; D008563:Membrane Lipids; D010743:Phospholipids; D009428:Netilmicin