STUDIES ON SULFATION FACTOR (SF) ACTIVITY OF HUMAN SERUM

Abstract

ABSTRACT An improved design of the in vitro bioassay of SF activity in human serum, based on the 35S-uptake of cartilage from hypophysectomized immature rats, has been evaluated. The method is based on a completely randomized block design, each assay statistically evaluable. The elimination of the error among the rats improved the mean precision (λ)rom 0.28 to 0.14. L̄ωas 6.3. The suitability of the design was shown in a series of 157 consecutive assays, in which 10 % had indeterminate confidence limits when P [2266] 0.05. The standard error of 13 replicate assays within one group was ± 1.9%. Six duplicate assays of sera of different SF activities on two groups had a mean difference of 0.09 SF units per ml. The sensitivity of the method was high, [2266] 0.005 units of SF activity, and permitted its application to normal subjects as well as patients with hypopituitarism. The response of the animal strain was stable for at least one year. The limits of the linear range of the dose-response curve with the local reference serum were 35 and 140 μl of serum. The serum factor was stable at −20° C for one year and at +18°C for one week. Although human growth hormone and glutamine in vitro significantly increased the 35S-incorporation, each of them could account for only a small part of the SF activity of normal human serum.