BIOASSAY OF HYPOPHYSEAL GROWTH HORMONE: THE TIBIA TEST1

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Abstract
A standard procedure for the bioassay of growth hormone, which utilizes the increase in the width at the proximal epiphyseal cartilage of the tibia of the hypophysectomized female rat is outlined. No significant difference was found between intraperit., intraven., and subcut. admn. of the hormone. Injn. periods of 1, 2, and 3 days were found unsatisfactory, whereas 4- or 5-day injn. periods produced a satisfactory response. A single daily injn. of hormone produced about the same response as injns. of the same total dose given twice daily. The min. significant increase in width of the cartilage plate was considered to be 30 u. The most satisfactory working range of the curve lay between approx. 190 and 314 u, which represented the cartilage response to doses of 5-120 [mu]g. of pure hormone. Within this range, and with groups of 8-10 animals, approx. doubling a given dose produced a significant increment in the response. The slope of the curve obtained with pure growth hormone approached that obtained previously with partially purified growth hormone. The specificity, sensitivity and accuracy of the procedure are discussed.