Human growth hormone
1—43 (hGH
1—43) is an amino terminal fragment of 22 kilodalton hGH (hGH
1—191). In the present study, we developed a specific sandwich-type enzyme linked immunosorbent assay (ELISA) of hGH
1—43. The minimal detectable dose was 3.5 × 10
−4 pmol/well. hGH
1—191 did not show any crossreactivity to hGH
1—43 in the assay up to the dose of 0.25 pmol/well. Using this assay, we investigated the quantitative relationship between hGH
1—191 and hGH
1—43 in contents of normal human pituitary gland and hGH-producing adenoma cells. We also studied the release of hGH
1—191 and hGH
1—43 from cultured hGH-producing pituitary adenoma cells. Means (±SD) ratios of hGH
1—43/hGH
1—191 in the cytosolic fractions were 0.02 ± 0.01% in the normal pituitary and 0.07 ± 0.04% in hGH-producing adenoma cells, respectively. In static experiments, the ratio of hGH
1—43/hGH
1—191 was 1.21 ± 0.50% in the culture medium of hGH-producing pituitary adenoma cells. hGH
1—191 and hGH
1—43 were released in parallel in response to TRH, and the hGH
1—43/hGH
1—191 ratio was 1.37% in perifusion experiments. These observations suggest that the hGH
1—43/hGH
1—191 ratio in cell content is much lower than previously reported. It was also suggested that the ratio of hGH
1—43/hGH
1—191 is higher in the releasable pool of hGH in the pituitary and hGH
1—43 might be secreted in a similar fashion to hGH
1—191.
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