Influence of endogenous and exogenous Jaffé-reaction-positive pseudo-creatinine chromogens in determination of creatinine in blood of normal and cephaloridine-administered rats.

To investigate a magnitude of analytic errors brought by certain interfering substances to the chemical method using Jaffé-reaction for determination of creatinine, two sorts of values determined by the chemical method and by the HPLC method were compared between each other, in blood samples obtained from control and cephaloridine (CER)-administered rats. The rats that received an intravenous injection of CER in dose of 1,000 mg/kg body weight, showed two peaks at the 1-hour and on the 3-day. Since the color development of CER determined in the chemical method showed that 1 g of CER corresponded to 0.0208 g of creatinine, the results of plasma CER determination proved that the first peak was ascribable to the color development of CER. As to the second peak, no significant difference was observed between the values of the two methods. This finding denoted that, when the creatinine levels were elevated, the two sorts of values due to the two methods approached to one another, and suggested that the ratio of "endogenous Jaffé-reaction-positive pseudo-creatinine chromogens" to "total Jaffé-reaction-positive chromogens" would be decreased according as the "true" creatinine was increased. In the control rats, the ratio to "total Jaffé-reaction-positive chromogens" was 60% in terms of "true" creatinine, and 40% in terms of "endogenous Jaffé-reaction-positive pseudo-creatinine chromogens."