Characterization of the site of cleavage of luteinizing hormone-releasing hormone under conditions of measurement in which LHRH degradation undergoes physiologically related change

The possibility that the degradation of luteinizing hormone-releasing hormone (LHRH) may contribute to the establishment of appropriate levels of the decapeptide neurohormone for gonadotropin release is of potential importance to this neuroendocrine regulatory pathway. We have recently provided evidence that total LHRH degradation undergoes a transient decrease in homogenates of the hypothalamic median eminence immediately prior to the luteinizing hormone surge during the first estrus cycle at puberty in the female rat. Total LHRH degradation in this situation was highly correlated with the appearance of LHRH_1-5. In order to more fully characterize LHRH degradation under these conditions of measurement, we have carried out an analysis of all LHRH degradation products by high performance liquid chromatography/amino acid analysis. Our findings suggest that LHRH degradation occurring under these conditions is due to cleavage at the Tyr⁵-Gly⁶ bond.