A new bioassay for insulin in conscious rabbits by continuous measurement of glycemic responses.
Because of the substantial variability often observed in the determination of insulin potency by the United States Pharmacopeia (USP) bioassay method, a large number of rabbits are required in order to attain an accuracy of +/- 6% and each bioassay needs 2-3 weeks to be completed. In this report, an improved bioassay method has been developed. This bioassay was conducted in conscious healthy rabbits. The decline in blood glucose levels, following intravenous injection of an insulin preparation, was monitored (in uninterrupted manner) by the continuous glucose monitoring system developed. A glucose response curve was generated, and from this response curve, various pharmacodynamic parameters were easily determined. The whole procedure could be completed in 1 day and also achieved an accuracy where upon only one rabbit is needed to determine accurately the insulin potency. To validate the method, a total of nine healthy rabbits were studied to determine the inter- and intra-animal reproducibility. The values of insulin potency determined from four pharmacodynamic parameters were compared, and the potency calculated from the ABGC (area of the blood glucose response curve under baseline) was found to be the most accurate: a mean (+/- SEM) value of 102.3(+/- 1.2)% was determined by inter-animal study (n = 9) and a value of 100.6(+/- 1.3)% by intra-animal study (n = 4). The inter-bioassay variability among the random-dose bioassays was 1.2% for inter-animal and 1.3% for intra-animal studies. The insulin potency in an insulin sample determined by this bioassay had attained an overall mean (+/- SEM) value of 101.6(+/- 0.8)% (n = 17).(ABSTRACT TRUNCATED AT 250 WORDS)
Lin
S
S
Controlled Drug-Delivery Research Center, College of Pharmacy, Rutgers University, Piscataway, NJ 08854, USA.
Chien
Y W
YW
D000818:Animals; D001681:Biological Assay; D001786:Blood Glucose / Q000032:analysis / Q000378:metabolism*; D005260:Female; D006493:Heparin / Q000494:pharmacology; D007328:Insulin / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology*; D011817:Rabbits; D011863:Radioimmunoassay; D012996:Solutions
D001786:Blood Glucose; D007328:Insulin; D012996:Solutions; D006493:Heparin