EFFECTS OF GENTAMICIN, NEOMYCIN AND TOBRAMYCIN ON RENAL CALCIUM AND MAGNESIUM HANDLING IN 2 RAT STRAINS

1. Standard renal clearance techniques were used to compare the acute effects of gentamicin, neomycin and tobramycin on renal calcium and ma gnesium handling in Sprague-Dawley and Fischer 344 rats. 2. Significan t hypercalciuric and hypermagnesiuric responses to all three drugs (P< 0.01) were apparent within 30 min of the onset of drug infusion. 3. Th e magnitude of the acute hypercalciuric and hypermagnesiuric response to the three aminoglycosides was comparable. This contrasts with their nephrotoxic action where neomycin >> gentamicin > tobramycin. The mag nitude of the acute physiological responses to these drugs do not ther efore reflect their nephrotoxic potential. 4. Sprague-Dawley rats were at least as responsive as Fischer rats in their acute renal responses to gentamicin. If Fischer rats are more sensitive to aminoglycoside n ephrotoxicity than Sprague-Dawley rats, this is not reflected in their acute responses to gentamicin.