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Elevation of Plasma LH Concentrations Induced by LH-Releasing Factor as Measured by Radioimmunoassay in the Sheep

Department of Physiology, Baylor University College of Medicine Houston, Texas 77025

Research supported by NIH Research Grants HD 02577, AM 08290, Training Grant GM 956 and FR 00254 to Common Research Computer Facilities, Texas Medical Center, Houston, Texas.

Abstract

With the use of a solid phase radioimmunoassay in which ovine LH can be detected in a concentration of 0.1 ng LH/ml, no immunochemical cross-reaction to a purified preparation of ovine LRF was observed at levels 1 x 10⁵ times greater than the minimum detectable concentration of LH. Biological activity of this preparation of LH-releasing factor (LRF) was studied by rapid intracarotid injection (100 µg) into mature rams (55 and 60 kg body weight) and subsequent assay of plasma LH by radio-immunoassay. Concentrations of plasma LH were found to rise 3 min after injection with a peak at 5 min, after which they returned to preinjection levels within 60 min. Intracarotid injection of purified ovine thyrotropin-releasing factor (TRF) as control produced no detectable changes of plasma LH levels measured by the radioimmunoassay. (Endocrinology 84: 1517, 1969)

Received December 5, 1968.