The stability in vitro of bioactive and immunoreactive LH in human blood and plasma

Abstract

The degree of stability in vitro of bioactive and immunoreactive LH in human blood, plasma and serum was examined. Bioactivity and immunoreactivity of LH were assayed by the dispersed mouse Leydig cell assay and by standard radioimmunoassay respectively, using the same reference preparation (first international reference preparation for human pituitary LH 68/40 for immunoassay). Bioactive and immunoreactive LH were stable in blood and plasma at 22 degrees C for up to 4 and 24 h respectively, and in blood at 4 degrees C for up to 24 h. There was no loss of biological or immunological LH activity in plasma which had been either snap-frozen and stored at -70 degrees C, allowed to freeze at -20 degrees C and stored at that temperature or kept at 4 degrees C for 24 h and then stored at -70 degrees C. Likewise, the levels of LH in plasma and serum which had been stored at either -20 or -70 degrees C and then thawed and refrozen up to four times remained unchanged. In addition, the biological and immunological activity of LH was not affected after vortexing samples of plasma or serum for up to 60 s. Bioactive LH was also stable in plasma samples after prolonged storage (up to 9 months) at either -70 or -20 degrees C. We conclude that LH bioactivity and immunoreactivity are stable in blood and plasma following a variety of treatments commonly experienced during normal handling of a blood sample after venepuncture.

Effect of Delays in Processing Blood Samples on Measured Endogenous Plasma Sex Hormone Levels in Women

“…Ellis et al (9) reported no statistically significant effects of storage for up to 24 h for FSH and LH, and Evans et al (10) reported no effects for up to 120 days when samples were kept refrigerated. Tsatsoulis et al (15) examined changes in LH when plasma was held at 4jC for up to 24 h in four male subjects and found little variation over time. Key et al (16) analyzed blood samples from 15 women and found increases in testosterone after 6 h of 1.0% (95% CI, À2.5% to 4.5%) in plasma samples and 5.2% (95% CI, 0.2-10.4%) in serum samples, and after 24 h slightly larger changes of 3.2% (95% CI, 1.4-7.9%) in plasma and 6.2% (95% CI, 0.2-12.5%) in serum.…”

Immunoreactive LH in long‐term frozen human urine samples

“…[36] Both the assays detect intact LH and some fragmented forms probably including the core beta fragment. [41] The quantitative reproducibility of the ICL immunoassay indicates it is more robust for measurements of urinary LH for anti-doping purposes compared with the IF assay. This could explain the consistently lower LH levels measured by the IF assay than the ICL assay.…”

“…Previous studies have reported that plasma LH is stable after storage for 8 and 14 days after refrigeration (4 C), [39,40] for 14 days stored frozen (-6 C) [40] and for up to 9 months after -20 or -70 C storage. [41] The quantitative reproducibility of the ICL immunoassay indicates it is more robust for measurements of urinary LH for anti-doping purposes compared with the IF assay. Nevertheless despite the quantitative reduction in urine LH by the IF assay, the reduction was proportionate over the four years frozen storage.…”

Analytical and clinical significance of peptide hormone heterogeneity with particular reference to growth hormone and luteinizing hormone in serum

“…That these changes are of physiological, and perhaps pathological, relevance is indicated by the substantial number of studies (reviewed recently in Wang, 1988;Wilson et al, 1990;and Tsatsoulis et al, 1991) showing changes in the pattern of gonadotrophin glycoform secretion in different biological situations. The effects of glycosylation on biological activity in vitro appear to be intermediate in importance compared with minor effects on immunoreactivity and the major effects on in-vivo function.…”

“…(c) The measurement of B : I ratios has been extensively used to characterize the structure-function relationships of LH (reviewed by Dufau and Veldhuis, 1987;Wilson et al, 1990;Tsatsoulis et al, 1991). Such studies need to be carefully evaluated for adequate evidence of parallelism and other tests of biometric validity.…”