Marked species specificity of guinea pig luteinizing hormone: Validation of a bioassay

The Guinea pig is a potentially interesting alternative small animal model for the study of the neuroendocrine regulation of reproduction. However, ap propriate gonadotropin assays are not widely available for this species. Th e aim of the present study was to validate a bioassay procedure for guinea pig luteinizing hormone (LH). The well-established interstitial cell-testos terone in vitro bioassays with the use of dispersed mouse or rat Leydig cel ls, successfully applied for measurement of LH from a variety of mammalian species, were found to be unsuitable for assay of guinea pig LH because of a marked species specificity of guinea pig LH. An alternative bioassay proc edure was established with the use of dispersed guinea pig Leydig cells. Th is assay has bean shown to allow for the assessment of serum LH response to exogenous gonadotropin-releasing hormone and of the expected spontaneous p ulsatile pattern of basal LH secretion, with an apparent mean serum LH puls e interval of 31.4 minutes and 51.9 minutes, in long-term castrated and sha m operated male guinea pigs, respectively. This bioassay can be a useful to ol for more intensive exploration of guinea pig reproductive physiology.