Clearance rate of gonadotrophin releasing hormone in peripheral plasma of the pig.

Gonadotrophin releasing hormone was administered as an intravenous bolus injection into four boars and four ovariectomized sows. Radioimmunoassay of concentrations of gonadotrophin releasing hormone in blood collected periodically after injection indicated a biexponential decline suggesting a rapid distribution to the extracellular fluid and a slower elimination by metabolism. A mean half-life value of 2.12 +/- 0.95 (SD) minutes was calculated for the first component and of 13.15 +/- 2.55 minutes was calculated for the second component of the decline in gonadotrophin releasing hormone concentrations. No significant difference was detected between boars and sows for half-life value of either component. In the four boars, luteinizing hormone values reached a peak in plasma 20 minutes after injection and that of testosterone at 90 minutes after gonadotrophin releasing hormone treatment.