Is BaF3 Bioassay Useful to Identify Patients with Bioinactive Growth Hormone?

Abstract

We analyzed the ability of the BaF3 cell line bioassay to select patients with biologically inactive GH. We first evaluated the biological response of the Ba/F3-hGHR cells to rhGH additional doses from 10 to 5000 pg/ml. The concentration points corresponding to the linear part of the curve were selected. We then analyzed a group of sera, diluted like the standard, including the entire range of GH concentrations that can be analyzed by bioassay. The serum/standard area below the curve ratio was calculated. Serum GH immunoactivity determined by IMMULITE/ GH bioactivity ratios was calculated. Our experimental data showed that GH-bioactivity/GH-immunoactivity ratios below 0.303 are indicative of a bioinactive GH molecule. This bioassay would recognize only extreme cases of GH bioinactivity, and it would not be a useful tool in the search for patients with altered forms of GH.

Development of a Bioassay System for Human Growth Hormone Determination with Close Correlation to Immunoassay

“…4). This close correlation has also been reported for the Ba/F3/GHR cell proliferation assay (23) although a recent study (24) reported that the correlation was not so good for the same assay; however, several reports concerning the ESTA bioassay showed that the bioactivity of GH at the secretory peak as obtained by the GH provocation test tended to be greater than the immunoreactivity (24,(29)(30)(31). The discrepancy between the bioactivity and immunoreactivity values in the ESTA assay may be due to transient changes in the distribution of different GH isoforms present in the circulation.…”

“…However, for detection limits lower than 1 ng/ml, they have poor sensitivity, leading to concerns regarding the quantification of the actual somatogenic activity of human serum samples (12). Moreover, a recent paper suggested that the Ba/F3 bioassay would not be a useful tool for identifying patients with altered forms of GH (24). The assay described here using the BaF-GM cell line was demonstrated to have the lowest detection limit thus far, with a detection limit of approximately 0.02 ng/ml for human serum samples, i.e., over 50 to 100-fold more sensitive than the abovementioned recent cell proliferation bioassay.…”