Abstract
The inactivation of antibiotics in tissue homogenate is an important problem in the field of chemotherapy. Serial estimation of the in vitro recovery rates of antibiotic activities in rat kidney homogenate kept at 0°C were made by bioassay (OKUBO's band culture method). And some examinations were made to explain the inactivation mechanism in the rat kidney homogenate, comparing these studies with the same studies on rat liver homogenate reported by GO.
The results obtained were as follows:
(1) The changes in antibacterial activity of the various antibiotics in the rat kidney homogenate could be divided into four groups:
1) CER, CEZ: No significant decrease in activity through 24 hours preservation.
2) PCG, ABPC, CBPC, MCIPC, CET, JM: Gradual decrease; no recurrence.
3) MINO, DOXY: Immediate decrease; no activity change to 24 ho urs.
4) TC: Gradual decrease followed by recurrence of activity after 24 hours. The recurrence phenomenon that GO called the change of PCG and TC in rat liver homogenate could only be found in the TC measurement.
(2) The rat kidney homogenate was centrifuged at 9,000 × G and divided into supernate and pellet suspension. As time passed, the supernate showed a change similar to that of the homogenate presenting a slightly higher recovery rate, but the pellet suspension did not.
(3) Similar results to those obtained by the supernate in
(2) were obtained by the centrifugal ultrafiltration, contradicting the interaction between the antibiotics and the tissue c omponents during the bioassay procedure. TLC/bioautography d enied the production of metabolites.
(4) The Kidney homogenate supernate was fractionated by gel-filtration with a Sephadex G-200 to yield three fractions. The activities of both TC and PCG were neither inactivatedn or changed in any of the fractions.
(5) No inactivations or changes in PCG and TC were found in the supernate obtained by ultracentrifugation (105,000 × G ) of the kidney homogenate.
