Determination of Pituitary Hormone Contents

This section describes the measurement of pituitary hormones in the context of repeated dose studies of 1-4 weeks duration. When performing an endocrine safety pharmacology study in rats it is advisable to determine pituitary hormone concentrations at autopsy, because in this species specific pituitary hormone assays are readily available. The time point two hours after last dosing is in general suitable, when changes in pituitary hormone contents need to be assessed. 

The skull is opened by scissors, the pituitary gland is dissected out, the posterior pituitary is stored separately, and the anterior pituitary is halved by 

Hormone concentrations in dilutions of pituitary homogenates are calculated from standard curves using the appropriate reference standard for rat pituitary hormones, sample data are calculated as hormone per pituitary gland or per pituitary weight (mg). Group means are calculated and the significance of differences is assessed by the appropriate statistical methods. 

This approach provides a fast and flexible assessment of several pituitary hormones, results may be compared with morphometric evaluation and immuno-histochemistry for one or several hormones of interest. 

CRITICAL ASSESSMENT OF THE METHOD Changes in pituitary hormone contents are frequently characteristic and may be followed up by measurement of hormone secretion profiles if required. Analytical methods for the rat are often also applicable to mice. For toxicology studies in dogs, preparation of the pituitary glands at autopsy may be performed, but is time-consuming and less advisable because of the small numbers of animals in such studies. 

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