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Inhibins are heterodimeric protein hormones secreted by the granulosa cells of the ovary in the female and the Sertoli cells of the testis in the male. Published research studies have assessed Inhibin B levels in Sertoli cell function, ovarian reserve and granulosa cell tumors. A two-step sandwich-type enzymatic microplate assay to measure Inhibin B levels within 3.5h is reported, and sample pre-treatment is not required. The assay measures Inhibin B in 50 μL of serum or Li-Hep plasma sample against Inhibin B calibrators (10-1000 pg/mL). The highly characterized antibody pair used in the assay measures 100% Inhibin B and no response was detected above the sensitivity of the assay with Inhibin A, Activin A, Activin B, Activin AB, AMH, FSH, LH or Follistatin 315 at the concentrations tested. The second generation Inhibin B assay was compared against two commercially available assays using 60 male and 60 female samples, ranging in age from 20 to 50 years. The assay showed significant positive linear correlations to Oxford Brooks Innovation (OBI) and Diagnostics Systems Laboratories (DSL) assays (r=0.99; P0.0001; and r=0.97; P0.0001), respectively. Method comparison to OBI and DSL resulted in the following slope and intercept (Gen II=1.03 OBI-6.77 pg/mL and Gen II=1.57 DSL+11.29 pg/mL), respectively. Matched serum and Li-Hep plasma samples (n=120) showed a correlation coefficient of0.99 and a slope of 0.97 with zero intercept. Total imprecision calculated on three samples and two controls over 40 runs, three replicates per run, using NCCLS EP5-A guidelines was 6.8% at 19.34 pg/mL, 4.4% at 76.03 pg/mL, 4.3% at 275.3 pg/mL, 5.4% at 99.88 pg/mL, and 5.7% at 363.9 pg/mL. The LoQ for the assay at 20% CV was 4.8 pg/mL. Dilution and spiking studies showed an average recovery of 90-110%. A highly specific, sensitive, simplified and reproducible microplate Inhibin B assay has been developed to measure Inhibin B in serum and Li-Hep plasma. The performance of the assay is ideal for investigation into the physiologic role of Inhibin B in both men and women.

Insulin-like growth factor-I (IGF-I) is a ubiquitous hormone that is secreted in both an endocrine and an autocrine/paracrine manner. IGF-I has conventionally been measured in serum; however, transdermal body fluid (TDF) remains as an unexplored biocompartment in which IGF-I also resides and may be more biologically relevant because of its proximity to tissues and cells. The purpose of this study was to compare IGF-I in serum versus IGF-I in TDF before and after 8 weeks of physical training. Twenty-eight healthy men (28 +/- 5 years old, 176 +/- 8 cm tall, weighing 83 +/- 11 kg) had TDF obtained by a novel, minimally invasive method that included the application of continuous vacuum pressure on forearm skin perforated with tiny micropores created by a focused beam from a laser system and also had blood obtained by venipuncture. An enzyme-linked immunosorbent assay measured total IGF-I concentrations. A repeated-measures analysis of variance (biocompartment x time) and Pearson Product Moment Correlation coefficients (Por = 0.05) were used for statistical analyses. Data are presented as mean +/- SE. Total TDF IGF-I was significantly lower than serum IGF-I both before (TDF, 91 +/- 6 ng/mL; serum, 375 +/- 17 ng/mL) and after (TDF, 83 +/- 5 ng/mL; serum, 363 +/- 19 ng/mL) the exercise training. Serum and TDF IGF-I values were not significantly different pre- to post-training. Serum and TDF IGF-I levels were significantly correlated pre-training (r = 0.41), but not post-training (r = 0.34). The percent change between serum and TDF was not correlated (r = 0.09). This study has demonstrated that total IGF-I can be sampled and measured in TDF via a minimally invasive manner and is appreciably (approximately 76%) less than total IGF-I measured in serum. Additionally, the IGF-I measurements in these two biocompartments were not closely associated, possibly indicating an uncoupled, rather than a linked, regulation of IGF-I among the body's biocompartments.