Changes in the Concentration of Luteinizing Hormone in Plasma of Rams Following Administration of Oestradiol, Progesterone or Testosterone

Fluctuations in the basal level of luteinizing hormone (lh) in the plasma of ewes have been measured by the radioimmunoassay technique (Niswender, Roche, Foster & Midgley, 1968; Goding, Catt, Brown, Kaltenbach, Cumming & Mole, 1969). Goding et al. (1969) and Bolt, Kelley & Hawk (1970) reported that the injection of oestradiol into the ewe caused lh release. In rams, however, the basal level of plasma lh is not well defined and any effect exerted by exogenous steroids on plasma lh is not known. This study was designed to measure the basal level of lh in the plasma of adult male sheep and to determine whether exogenous oestradiol, progesterone or testosterone would alter the basal lh level. Sixteen sexually active Rambouillet rams, weighing about 100 kg and ranging in age from