DETERMINATION OF ISATIN, AN ENDOGENOUS MONOAMINE-OXIDASE INHIBITOR, IN URINE AND TISSUES OF RATS BY HPLC

1. We have previously identified isatin as one of the endogenous monoa mine oxidase (MAO) inhibitors in the urine and the brain of stroke-pro ne spontaneously hypertensive rats (SHRSP), using gas chromatography m ass spectrometry (GC-MS). 2. In this study, we attempted to develop a convenient assay to determine isatin using high performance liquid chr omatography with an ultraviolet detector (HPLC-UV). The standard curve for authentic isatin was linear at a range from 2 to 20 nmol per ml, The coefficient of variance was within 3% for both intra assay and int er assay. The sensitivity was 20 pmol per 10 mu l of urine sample.3. I satin concentration correlated significantly and positively with endog enous MAO activity (tribulin-like activity) in both urine (r = 0.924, P < 0.001) and kidney extracts (r = 0.862, P < 0.01). There was a sign ificant difference in urinary isatin between Wistar Kyoto rats (WKY) a nd SHRSP. Oral administration of isatin increased urinary isatin conce ntration and systolic blood pressure in WKY. 4. Determination of isati n using HPLC-UV may be useful for elucidating role of isatin in variou s conditions of stress and disease. (C) 1998 Elsevier Science Inc.