Quantitative immunocytochemistry of hypothalamic and pituitary hormones: validation of an automated, computerized image analysis system

Abstract

A limiting factor in the use of immunocytochemistry in experimental endocrine studies has been the lack of a suitable procedure for quantification of immunoreactive hormones. The objective of the present study was the development of an automated, computerized image analysis system adapted to the quantitative analysis of light microscopic immunocytochemical reaction product. Reaction conditions that result in optimum, standardized, and quantitatively linear development of reaction deposit are described for H2O2 and diaminobenzidine concentrations, antiserum dilutions, and substrate incubation times. In addition, evaluation techniques, including the use of a standard control section to monitor variance and incorporate it into the statistical analysis of the results are documented. For each of the reaction variables, the immunostaining was linear over the range of specific staining. When the optimum conditions were exceeded, marked over-estimations of hormone levels occurred due to the detection of nonspecific background features reaching the detection threshold. Application of this quantitative immunocytochemical (QICC) method to the analysis of variations in hypothalamic and pituitary hormone levels was validated by comparing values obtained with QICC to those with radioimmunoassay (RIA). The relative changes in both hypothalamic gonadotropin-releasing hormone and pituitary luteinizing hormone induced by manipulation of gonadal steroid levels, as measured by RIA and QICC, were highly correlated. Two-way analysis of variance revealed that the two techniques were not significantly different in their detection of changes in either hormone. Thus, under optimally defined conditions, quantitative immunocytochemistry using computerized image analysis has been validated for the accurate measurement of pituitary and brain hormones in precise regions.