Release of LH and FSH in the normal intact ram by synthetic LH-RF and the effect of pretreatment with testosterone propionate.

Abstract

were made every 5 min for at least 20 min before the rapid intrajugular injection of LH-RF and then for a further 45 min. Samples were also taken 60 and 90 min after injection and, when 50 \g=m\g LH-RF was administered, the period of frequent sampling was extended. All experiments began at approximately 14.00 hours and at least 3 days were allowed to elapse between experiments. The TP (Koch Light, Colnebrook, Bucks) was administered by intramuscular injection in arachis oil in a 50-mg dose at 09.00 hours and again at 18.00 hours on the first 2 days followed by 100 mg at 09.00 hours on the 3rd day. The res¬ ponse of rams pretreated with TP to a dose of LH-RF was compared with the response to the same dose of LH-RF (7 days earlier) in the same animal pre¬ treated with vehicle only. Plasma LH was assayed by a double antibody method similar in procedure to that of Niswender, Reichert, Midgley & Nalbandov (1969). An equine anti-bovine LH, preabsorbed with bovine TSH (Snook, Saatman & Hansel, 1971) was used at a final dilution of 1 : 200,000. Ovine LH (LER 10 56)