PLASMA-CLEARANCE AND TISSUE UPTAKE OF NATIVE AND DESIALYLATED EQUINE GONADOTROPINS

Equine luteinizing hormone (eLH), equine follicle stimulating hormone (eFSH) and equine chorionic gonadotropin (eCG) were desialylated and their plasma disappearance, tissue uptake and degradation determined. Both native hormones and their desialylated derivatives were radioiodinated and injected intravenously into male rats. Plasma samples were taken at different time intervals and examined for both total and tricholroacetic acid (TCA) precipitable radioactivity. Disappearance curves for each hormone consisted of two exponential components: a fast clearance followed by a slow phase. The apparent t1/2 of the fast component for native eCG, eLH and eFSH were 18.3 min, 17.0 min and 17.1 min, respectively; this is in contrast to their desialylated derivatives which had a t1/2 of 2.8 min, 4.9 min and 7.1 min, respectively. The slower component for native and desialylated eCG had a t1/2 of 355.5 min and 171.2 respectively. After TCA precipitation more than 90 percent of the radioactivity in plasma was in the pellet, whereas in urine almost 95 percent of the radioactivity was in the TCA supernatant. Coincident with the disappearance of the hormone from the plasma its uptake and release was observed in liver, kidney, testis, and muscle tissue. Gel filtration data on contrast with the latter. Together these results indicate that eLH, eFSH and eCG disappear from the plasma of male rats in a biphasic manner with a rate slower than their desialylated derivatives.