Species Differences in Follicle-Stimulating Hormone as Revealed by the Slope in the Steelman-Pohley Assay1

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Abstract
Follicle-stimulating hormone (FSH) preparations from 5 different species sources (porcine, ovine, human, rat and equine) were tested by the HCG-augmentation assay of Steelman and Pohley. Each FSH preparation was injected according to both of the following schedules within each assay: a) twice daily injections for 3 days; b) single daily injections for 3 days. Reduction of the daily injections from 2 to 1 caused a decrease in the mean value of the slope for FSH from all species. However, the magnitude of the decrease in the slope for porcine FSH (47%) was at least twice as great as that for FSH from the other species (15–23%). The critical effect of the number of daily injections on the slope of porcine FSH suggested a qualitative, biological difference between this hormone and FSH from the other species tested.